Chocotto Sister: Yurika Hanayamada

 A young girl who appears to be younger than Choco. She is from a rich family and lives in a big house with a maid who tends to her. To live to her standards, she is often forced to take violin lessons, tutor, English conversation lessons, which she dislikes. During one of her attempts to escape her lessons, she met Choco and they became friends. Even though in the beginning, she did not really like Choco, she came to really care for Choco as they got to know each other better. However, Yurika is not good at showing her true feelings and often denies this. Also, Choco gave her a nickname, "Yuri-pyon", to which she objected at first but got used to. She has a crush on Kakeru but he is oblivious to her feelings. 

Chocotto Sister: Ayano Sonosaki

 A woman who works in the Ciel blue de fleur (which seems misspelled early on in the anime—it should probably be the French "bleu" instead of the English "blue": "Blue heaven of flowers") near Tsabuki manor. Ayano's dream has apparently always been to open her own flower shop. Haruma has a crush on her, but has so far been unable to work up the nerve to do anything about it. It seems that she remains oblivious of Haruma's affections and sees him as no more than a good acquaintance. She was engaged to Kazuya until he broke it off, to her considerable sorrow.Ayano runs a small florist shop near where Haruma lives.

Genshiken: Kanako Oono

 Kanako is the fourth president of Genshiken. Raised in the United States since the third grade, she graduated from an American high school, joining the Genshiken at the beginning of the Fall term. Normally soft-spoken and easily embarrassed, Kanako is surprisingly upfront when it comes to one of her two main passions: cosplay. With a nice figure and large bosom, Kanako and her cosplaying (using costumes sewn personally by Tanaka, whom she begins dating) quickly become Genshiken's main attraction at student fairs. Kanako's other main passion is yaoi involving muscular, middle-aged, exceedingly bald men. One of the reasons Kanako joins Genshiken in the first place is because only they would accept her fetish. She is also close to Saki, as Saki was the first one to find out about Kanako's preference for older men.

Kanako is against cosplay sex, claiming that doing so betray the characters, but when asked if it's okay to have sex while cosplaying as a porn character, she becomes very embarrassed and indicates she has already used that loophole. Her decision to become the next president of Genshiken comes from Saki's suggestion that she could turn it into a cosplay club (literally "Society for the Study of Cosplay" in the original Japanese). Kanako later passes the presidency on to Ogiue. In the relaunch of the manga, it is revealed that she is not job hunting as she is waiting for Tanaka to finish his additional schooling, implying that she may be planning to be a housewife or to help him.

Ya Boy Kongming!: Nanami Kuon

 Nanami Kuon is a bassist and is first seen busking on the streets of Shibuya. After encountering Eiko Tsukimi, they both grew close through their mutual love of music. She is a talented singer and bassist. Her skills even won the praise of Eiko.

Garo Vanishing Line: Sophia Hennes

 A red-haired teenager living at the Katrina Home who is looking for clues about her missing brother whose disappearance is connected to "El Dorado". Her search brings her in contact with a horror and eventually saved by Sword, who is also looking for El Dorado. She has since followed Sword and helped him hunt Horrors using her knowledge of the internet. It has since been revealed that the King of El Dorado wishes to recruit Sophie for an as-of-yet unrevealed purpose.