Koreyuki Tani (谷 惟之 Tani Koreyuki) is a first-year student of the Kamiyama High School and a member of the school's Go Club.
He's a bit smug and a little arrogant.
He has light brown hair cut into a bowl-shaped haircut and brown eyes.
Before Satoshi goes up to his designated buzzer for the Quiz Trial 7, one other participant calls to him. Satoshi recognizes that this person is "Tani-kun" from the Go Club. Before they can talk about something interesting that happened in the Go club, Satoshi has to go and introduce himself to the crowd. Koreyuki and Satoshi lose in the Quiz Trial, and then Koreyuki informs him that the Go Club had some playing stones chosen. He then challenges Satoshi in the cooking competition that was set for the next day. Koreyuki loses the cooking comeptition to Satoshi.
He then appears as one of the wannabe dectectives trying to rat out Jūmonji.
Koreyuki sees himself as Satoshi's rival. Though, by the looks of it, Satoshi only finds him annoying.