Hikari Tsutsui (筒井 光 Tsutsui Hikari?) is one of two protagonist of the 3D Kanojo series.
He has shaggy black hair and glasses. He's usually seen in a cyan tie with a white shirt, and navy dress pants.
Tsutsui is an otaku who finds love where he least expects it: a beautiful girl named Iroha who he initially states represents everything he hates about 3D girls. Although Tsutsui is at first skeptical of everything to do with the relationship, Iroha addresses him with nothing but kindness and the two become a couple. Tsutsui must navigate the barricades of his own insecurities while dealing with his new love life and carefully discovering people who can truly be his friends. He's finally able to find a glimmer of happiness in a life he previously lived in isolation and rejection, but he has to make due with the time he has because there's a catch: Iroha, the girl who has changed his life, is moving in 6 months!
Iroha Igarashi is Tsutsui's girlfriend. When they first met, Tsutsui was a bit angry at her because she was "all of the things that he hates about 3D girls." But after Tsutsui saved her from her ex-boyfriend, she began to grow feelings for Tsutsui and eventually she asks Tsutsui to be her boyfriend. She is fond of teasing him. She has also nicknamed him Tsutsun. On a somewhat good manner, she is very protective of him, even going as far as to nearly beat up the boys teasing him for being an otaku and even when he was framed for being a lolicon, she still insisted on going home with him after classes, even though he wanted her to avoid him because it might damage her reputation.
Ito is Tsutsui's first and best friend, who also happens to be an otaku. Ito and Tsutsui are quite close, Tsutsui going so far as to cancel plans with Iroha to make sure he does not neglect Ito. Ito expresses no jealousy towards Tsutsui for having Iroha as a girlfriend, and embraces everything in Tsutsui's best interest. Ito is one of only two people (the other being Iroha) who stays on Tsutsui's side and believes in him when he's labeled a lolicon.
Arisa is a classmate of Tsutsui. Initially, when Arisa first meets Tsutsui when he helps her up after she's fallen, she acts like all other girls and addresses him with disgust. Tsutsui is not disheartened by this reaction, however, noting that he is used to this type of rejection. However, later on and seemingly moved by his initial kindness, Arisa approaches Tsutsui after seeing him moping after classes during times when he has love troubles with Iroha and asks him (in a less-than friendly way) what his problem is. She chooses to lend him a listening ear on several occasions when he seems to be down, lends him some advice, and even offers to cut his bangs much to the jealousy of Iroha. Arisa displays a very mild tsundere personality, since she looks down on Tsutsui at times while others she expresses how lucky Iroha is to date a nice guy like Tsutsui, after he tried to comfort her during her distressing situation with her ex. Tsutsui later goes so far as to call her "his only female friend" and she becomes a regular part of the group. It is not explicitly stated, but somewhat implied that he is also her friend, although she does not seem to express any romantic interest in him.
The younger brother of Tsutsui, who is the classmate of the younger sister of Tsutsui's bully Mitsuya. Tsutsui does not have a very close relationship with his brother, Kaoru. There are times when Kaoru seems to "secretly" encourage Tsutsui when suggestive things happen in Tsutsui's room with Iroha, although Kaoru does not have much faith in his brother. In a time of major duress, Kaoru thinks of the damage to his own reputation instead of rallying to his brother's aid for support, and explicitly mentions that he does not want to grow up like Tsutsui.