Tadakuni

Tadakuni is a student at Sanada North Boys High who acts as the straight man of the group. He has a younger sister whom he hardly talks to and who is stronger than him and his friends. He also works part-time at a pizza restaurant. His last name remains unknown.

He appears the least in the whole anime series due to his "ordinary" appearance and personality. And this was told in the intro of Episode 10, where the other boys conclude that he doesn't get much time on the screen because he's too normal and uninteresting.

Appearance
Tadakuni is a slim teenager with relatively short black hair. Like his friends, he is usually seen in his school uniform except when working part-time.

Personality
Tadakuni acts as the straight man of the group. He is usually involved in Hidenori's and Yoshitake's wild ideas despite his disapproval. He is good at making up stories that notably excite the other two. Despite being introduced like a main protagonist, he gets the least roles in the trio and even, at one point, not show up for a full episode. Tadakuni seems to be quite normal and at times not very well-versed in general knowledge, as seen when they were all playing ping-pong. He likes to sometimes mess around with his sister's underwear with Hidenori and Yoshitake when they are at his house.

Nago-san
Nago is Tadakuni's friend and co-worker at Pizza-Le, whom he addresses with the honorary suffix -san. He respects her knowledge and judgement regarding various matters and is generally seen asking her a question. He does not mind opening up to her about his worry that his friends neglected him, showing them to be quite close. In addition, both Tadakuni and Yasunori seem to be smitten by Nago's alternate appearance - the Convex Mirror girl.

Yoshitake and Hidenori
His best friends.

Despite the fact that he often doesn't understand some of their roleplays and maintains a sense of reality no matter how into the game the other two are getting neither ever chastises him for ruining the game or for taking the fun out of it. Rather, Tadakuni's 'one clueless character' is a common trope in their 'adventures'.

They always seem to enjoy his company, but Tadakuni feels a great amount of isolation in the trio at certain stages, feeling like he's the odd one out or that they might be holding themselves back around him because he's not on their wavelength.

Tadakuni seems not to be able to read the atmosphere as well as they do, getting punched by the Literary Girl when he interrupts them as they make up great serious lines to fulfill her dreamy romantic encounter ambitions (not realizing at this stage that she wants inspiration for her book) yelling that there is a sale for potato chips. Hidenori, however, recognised this as Tadakuni reading the situation accurately and trying to subvert it. In another instance, he tries to assist the overly self-conscious girl when she kept embarrassing herself.

He always shows great courage when he thinks about trying to be better friends with them never giving up despite his paranoid self isolation - although sometimes he mistakes them for another unknown pair while trying to talk to them.

Tadakuni's younger sister
They don't have a good relationship and it's said that they talk to each other maybe once a month.

Tadakuni, despite his "normalcy", goes along with pranks involving her underwear.

She tends to listen in on his conversations with Yoshitake and Hidenori and it's because of this that she also gets carried away by his made up stories.