Kosaka appears to be a rather gentlemanly and kind person. He also appears to be smart, as he was seen tutoring an unnamed girl who was assumed to be his girlfriend.
In episode 3, Kosaka bought Tomoko an umbrella when it was raining, although she did not seem to notice what he had done. In episode 8, Tomoko meets him again. Her cousin, Kī, believes him to be Tomoko's boyfriend after a lengthy lie. After Kī found him with a girl he was tutoring, she demanded an apology for hurting Tomoko, thinking that he was cheating on her. After Tomoko requested that she be left alone with him, Kī found out that Kosaka was not actually Tomoko's boyfriend, she began treating Tomoko differently. Kosaka has never made another appearance in-person since then.
Kosaka looks rather feminine compared to some of the other male characters in the series. He has a thin build, gray eyes, pale skin, and short black hair.
Strikethrough episodes or chapters indicate the character was mentioned but did not make a physical appearance)
Kosaka has reached out to Tomoko to show her some kindness. Unfortunately, after Tomoko lied about Kosaka being her boyfriend he views her as a strange girl and has not been seen since.
- Kosaka is older than Tomoko.
|Female Characters||Tomoko Kuroki | Yū Naruse | Mrs. Kuroki | Kotomi Komiyama | Megumi Imae | Kiko | Ogino | Yuri Tamura | Masaki Yoshida | Mako Tanaka | Emiri Ucchi | Hina Nemoto | Akane Okada | Asuka Katō | Shizuku Hirasawa | Akari Iguchi | Sayaka | Koharu Minami | Hikari Itō | Futaki | Miyazaki|
|Male Characters||Tomoki Kuroki | Mr. Kuroki | Kakinuma | Yoshinori Kiyota | Kosaka | Hatsushiba | Suzuki | Jun Ishimine | Homeroom Teacher | Art Teacher | Aomatsu | Yocchan | Nico Tanigawa | Wada|
|Manga Volumes||01 | 02 | 03 | 04 | 05 | 06 | 07 | 08 | 09 | 10 | 11 | 12 | 13 | 14|
|Anime Episodes||01 | 02 | 03 | 04 | 05 | 06 | 07 | 08 | 09 | 10 | 11 | 12 | OVA|