Osamu Osanai (
Osamu is a short boy, with a black hair and a bowl haircut. He wears large square glasses, which his reflection usually obscures his eyes. He usually wears his school uniform, consisting of a white button-up shirt with a chest pocket and pants.
While gender-swapped, Osamu maintains a similar appearance but with a bob haircut and wearing the female school uniform.
Osamu has expressed on several occasions his preferences for small breasted little girls over large breasts. He likes to draw, being a member of the school's manga club, always keeping his sketchbook on him and sketching things of interest. Osamu himself states wherever he is he will always be sketching.
When Kazuya Kagami awakes from his dream and accidentally gropes Chisato Chikaishi's breasts upon doing so, Osamu and Shirou Shiramine talk about him as Chisato berates Kazuya. Chisato eventually turns her attention towards the two for talking about her breasts, and knocks them out with her harisen, giving Kazuya the chance to escape. The next day, after Kazuya is late to school, the two listen to Chisato berate Kazuya again.
Osamu loans Shirou about 500000 yen to help him pay off his restaurant bills, making a deal to have Shirou repay him later. In class, he watches Shirou dropkick Kazuya as Shirou blames him for the debt he has incurred. During lunch, they find everyone's lunches has disappeared, when Kokuyou suddenly bursts in shouting for Kazuya and incidentally revealing herself to be the culprit. Kokuyou initially identifies Osamu as Kazuya incorrectly while Shirou recognizes Kokuyou as the woman who left him in debt at the restaurant. Kokuyou and Kiriha get into an argument and move to the school rooftop to settle it with Tsuzura Temple style arm wrestling while the class watches. While they arm wrestle, Osamu sketches them until they are interrupted by a teacher.
One day at school, Osamu finds Kazuya with Tadataka Tadata and Kiriha, inquiring who Kiriha is. When Kiriha claims to be Kazuya's master, Osamu tells Kazuya he is very lucky while Kazuya attempts to make up an excuse. Tadataka finds the entrance to the TRPG club they were searching for is missing. Kiriha detects something amiss with her Hazakura, and the groups walks down the hallways until they are met with unusual dead end. Nakajima reveals himself and threatens Tadataka to make his TRPG club an officially recognized club but Tadataka refuses. Nakajima summons a minotaur with his notebook amasogi, forcing the four to flee until they reached another dead end. Breaking into a nearby classroom, they use water and fire extinguishers to wash the minotaur away, weakening it. Kazuya uses up the last of the fire-extinguisher to clear the dead end wall only to be met with another wall. Kazuya defeats the Minotaur and they confiscate Nakajima's note book. Osamu plays around with Nakajima's note book a bit, as they review what Nakajima has done and his amasogi's ability. Kiriha returns the notebook to Nakajima and Nakajima destroys the notebook but summons another Minotaur with a page he kept hidden. Osamu reveals that it was actually his notebook that Nakajima destroyed earlier, using Nakajima's amasogi against him by creating a dragon to destroy his minotaur and accidentally setting off the school fire alarm. After school, Kazuya fills Osamu in on the paranormal happenings around them and requests he keep it secret.
Kazuya seeks Osamu's advice when the school becomes under the influence of Hiroshi Ohkado's amasogi. Osamu explains the gameplay mechanics of Pure Heart and he devises a plan for Kazuya to win Chisato back. While trying to Chisato back, Kazuya makes several mistakes and Osamu tells Kazuya one last trick he can use to win known as the Plunder Combo. With Osamu's trick, Kazuya' successfully wins Chisato back from Hiroshi who runs away crying. While Kazuya and Chisato stay in the nurse's office, Osamu and Kiriha go after Hiroshi who reveals his amasogi to be located in the computer room. Osamu realizes that means Hiroshi was using a PC version of the game which is X-rated, containing pornographic content. Osamu and Hiroshi rush to the amasogi's location where they destroy it. The next day, Osamu inquire from Kiriha how far Kazuya and Chisato went before they stopped the amasogi.
One day at school, Osamu, Kazuya and Chisato are called by Tadataka to his office. At the office Tadataka trips, revealing his baldness beneath his wig, which Kiriha explains to be a result of Curse Backlash. Tadataka then explains the reported sightings of the ghost of Eiko Nago for them to investigate. The three students ask around the school for clues about Eiko. After compiling together their collected information, Tadataka and the group head to question the members of Yuuichi Nishina fanclub which Eiko was a member of. There they encounter Nanako Nanakai who is inquiring about the same topic for her newspaper club, when suddenly Yuu Osakabe is suddenly assaulted by a figure resembling Eiko. Kazuya saves Yuu but the figure escapes. The group bring Yuu to the nurse's room where they question her. Returning to Tadataka's office, they review their new information when one of Tadataka's subordinates bring them information of Eiko's sister. They discover Nanako was Eiko's sister and had her family name changed after a divorce. The group rush outside to intercept Nanako, with Kazuya and Kiriha getting ahead with their abilities. By the time Osamu, Chisato and Tadataka catch up, Kazuya had already defeated the amasogi. Osamu then sketches Kiriha punishing Kazuya for not listening to her.
The day after the incident, Tadataka reviews the case with the group. Nanako arrives, revealing she has gone mute as result of the curse backlash. The group go their separate ways, with Osamu going to his manga club.
The day Kiriha officially transferred to Kazuya's school, she is immediately bombarded with questions from classmates and casually reveals herself to be living with Kazuya and says she has bathed with him. Shirou and the students form a trial to judge and punish Kazuya for his crimes. Osamu testifies against Kazuya, stating Kiriha told him that Kazuya had shoved his finger up her anus. Kazuya is ultimately found guilty and tortured. After class, Kiriha and Kazuya gather Osamu, Shirou and Chisato to form a Counselling club. Kiriha explains in details various things concerning curse, Aberrations, amasogi, and Kazuya being a Taboo Child. Osamu, Shirou and Chisato agree to help, with Osamu still remaining a member of the manga club while doing so. Tadataka and Nanako arrive to pledge their support as well.
Osamu works on the computer as the club members listen to a students request only to find it to a complaint about Shirou's behaviour. After punishing Shirou, Osamu and the group go over some paper help requests but do not identify any of them to be amasogi related. Shirou leaves to ask a girl out. The next day, Osamu and the group congratulate Shirou on getting a girlfriend only for Shirou to explain he mixed up who he had sent his letter to. Later that day, Shirou discover his girlfriend Mitsuri Mizushima to be harbouring an amasogi. The group split up to gather info on where she ran to with Osamu contacting Nanako for information. They are unable to find Mitsuri, forcing Kiriha and Kazuya to go to her house but to no avail. Osamu and Kazuya's friends call him on the phone, having identified one of the previous requests as being from Mitsuri along with other information on her. One week later after the amasogi was dealt with and Mana Manaka was revealed to be the true user, the group converse about the case in the office.
Upon noticing a suddenly increasing cases of absent students at their school, Kiriha calls the group to the office to discuss the situation and introduce Kukuri as their new club advisor. Though Shirou is disappointed by her appearance, Osamu begins sketching her.
The next day, they find the number of students absent to have increased once again.  Meeting with Tadataka to go over the attendance records, Kazuya, Kiriha and Kukuri head out to investigate the first three cases of absences but return with no progress. Kazuya realizes the amasogi owner to be their teacher Isuzu Iriha herself, and goes to confront her with Kiriha. Isuzu falls unconscious and they return her to her home which they investigate. Having located the pillow amasogi but being unable to destroy it without severe repercussions, Kukuri introduces the group to Bakura. Bakura explains that they will be entering the dreamworld to destroy the persuade Isuzu to destroy the pillow from within the dream and warns them of the various dangers. In order to make sure they realize they are dreaming within the dream, Osamu writes into his sketchbook a reminder that they are in a dream, so when he opens it in the dream world they will be reminded. Osamu, Chisato and Shirou joining Kazuya and Kiriha in entering the dream world while Tadataka stays in reality to keep things in check. Within the dream world, the group go about their school day as normal but gender-swapped, unaware they are in a dream. In the club room, Osamu and Shirou converse about men, opening his sketchbook to draw Shirou getting courted. Upon doing so he finds the message he had written to himself and reminds everyone they are in a dream and go to confront their teacher. Osamu, Shirou and Chisato head to Isuzu's house to obtain her pillows only for it to be revealed to be fake and disappear. Kazuya and Kiriha are forced to fight their Shadow selves, breaking through the school.
As Kazuya and Kiriha fight their shadows, the three discuss what to do next. Osamu advises against splitting up and searching since the real pillow would obviously be hidden somewhere or even disguised. Suddenly an unfamiliar girl shows up requesting they help her kill Isuzu. While they initially ignore her, she reveals that the Isuzu they confronted to be a shadow with the amasogi hidden within her. Osamu secretly realizes the girl to be the real Isuzu and convinces the group to continue listening to her explanation. Just as they agree to cooperate, Shadow Isuzu appears before them. Shadow Isuzu creates shadows of Osamu, Chisato and Shirou to attacked them but they are saved by the girl who reveals herself to be the real Isuzu. Shadow Isuzu sends mores students to attack them but with Isuzu's help, they manage to escape. After escaping, Isuzu separates from the three to confront her Shadow herself. The three arrive just as Isuzu is losing to her shadow self, saving her with omamori given to them by Kukuri, allowing them to summon amasogi. Osamu uses his sketchbook to summon a tentacles monster to restrain shadow Isuzu who escaped by transforming into a giant spider causing the real Isuzu to faint. After the tentacle monster and Chisato's book golem is destroyed, Osamu summons a dragon to fight but it is also defeated. Osamu and Chisato are caught but rescued by Kazuya and Osamu and Chisato attempt to wake Isuzu. Osamu and Chisato provide support with their amasogi, allowing Kazuya to open a weak point in the spider, revealing the pillow for Isuzu to destroy. With the amasogi destroyed, Bakura informs them to go to sleep and they will reawaken in the real world. Osamu goes to sleep at Shirou's house. There Shirou finds he is unable to get turned on by his female self and tries to do so with Osamu's female self. Shirou has his way with him and Osamu tells Shirou that he is adding a hundred more pages worth of toning to his debt.
Akito Ashimine and Mimane Miyou introduce themselves as the newest members of Kazuya's club. For their first mission, the group head out to deal with a hikikomori amasogi on their school premise. Osamu sketches Mimane during the case until it is resolved. Some time later, Sunao Sumeragi transfers to their school and introduces herself to the club. Kazuya explains that Kukuri was assaulted by tsugumomo from Mayoiga the other day, with Sunao arriving as backup. Upon hearing she is staying with Kazuya, Shirou strangles him for being so lucky. Osamu states that Kazuya has already bathed to Sunao, Kazuya surprised that Osamu knows. The group then heads to the gym where Osamu, Shirou and Chisato watch Kazuya and Kiriha spar with their tsugumomo.
Drawing Skills: Upon seeing Kiriha for the first time, he had already finished a nude sketching of her while greeting her. Unlike Nakajima who had to draw his monsters in advance to summon later, Osamu was draw a more highly dragon on the spot and summon it using Nakajima's amasogi.
Keen Intellect: Of Kazuya's school friends, Osamu has demonstrated to be the smartest amongst the group and is quick to understand the various paranormal phenomena explained to him. When dealing with Nakajima, Osamu had the foresight to swap their sketchbooks, securing their victory over him. He is the first come up with a plan to make the group realize they are within the dream world before entering. Osamu was the only one to realize Isuzu was concealing herself as the young girl in the dreamworld and that directly outing her would alert Shadow Isuzu. He correctly deduces the pillow amasogi to be hidden and disguised within the dream world, realizing splitting up to blindly search for it would be waste of time.
Incarnation Sketchbook (具現化スケッチブック, Gugenka Suketchibukku): Though not his own amasogi, Osamu made effective use of Nakajima's own sketchbook amasogi against him. Using the omamori upon entering the dream world to summon the amasogi closest to them, Osamu summoned this one despite not actually being the owner, allowing him to temporarily use its abilities again. Osamu's great drawing skills allow him to make effective use of this amasogi.
- Flare Dragon (フレア ドラゴン, Furea Doragon): One of Osamu's go-to drawings, Osamu summons a giant dragon capable of blasting fire from its mouth.
|Faculty||Isuzu Iriha • Meotoike • Nieda • Kukuri Shirayama|
|First Year Students||Nanako Nanakai|
|Second Year Students|
|Third Year Students||Tadataka Tadata • Yuuichi Nishina • Yuu Osakabe • Sakumi Muratsuki|