Name: Fuyuki (フユキ)
Voiced by: Miho Saiki
First Introduced (Manga): Never
First Introduced (Anime): Minami-ke: Okawari Episode 04
An anime-original character, introduced and only present in Okawari. A lonely transfer student, he appears to be neglected by his never-present father, who is also the reason he must continually move. His personality is extremely repressed, and he seems entirely unable to refuse any favor asked of him. This latter characteristic is continuously exploited, something which annoys Chiaki to no end. Sensing his unhappiness, Chiaki seems to make a few half-hearted attempts to break his shell, but his complete lack of a response puts a damper on this. Likewise, Kana and Haruka's efforts bear similar fruit. He moves, leaving the show, in Episode 12.
Fuyuki likely has some sort of strong attachment to Chiaki, but it is highly doubtful that she reciprocates. See here for a discussion of this.
By far the most salient fact regarding Fuyuki is the fanbase's absolute hatred for him. Even the least spiteful of observers find him a major drag on every scene in which he is included, a drag on the show as a whole, and completely without redeeming features as a character; it is ironic, and true, that his only good scene was the one where he left. He is the only anime-original character, and has the dubious distinction of being the only character to be neither fun nor energetic. A stick-in-the-mud, in other words. Elements of the fanbase have chosen to practice selective amnesia about his existence, one of the most damning things that can happen to a character.
There is speculation, given the trend of episodes around Minami-ke: Okawari Episode 06, that Asread originally intended Fuyuki to play a much greater role, and for a possible pairing to decloak slightly, but furiously backpedaled after seeing the online backlash. Certainly, the later half of the season, which is much more similar to season one, does have some of the feel of a hasty retreat. If true, one wonders what they were thinking, especially since there's already a perfectly good possible incipient pairing in the actual manga for fans to ponder.