How to start this story
Follow the already accessible stories of the Dance Club, Robotics Club and the Ijincho Hounds.
In Chapter 4 earliest, after dealing with the Ijincho Hounds the first time, there's a group of students thanding in front of the MRC entrance.
HELP THE KID WHO'S GETTING SHAKEN DOWN
Talk to the students in front of the MRC.
Talk to Toki at the MRC.
LEARN THE BASICS OF VF5FS FROM TOKI
Head to the e-Sports Club room in the 4th floor and learn how to play Virtual Fighter 5 Final Showdown.
TALK TO OTANI IN THE CAFETERIA
The cafeteria is on the first floor.
CONTINUE INVESTIGATING THE E-SPORTS CLUB
Go back to the club on the 4th floor.
BEAT UP THE GUYS
Talk to Toki to play against Fujiwara, Uozumi and Yoshiba so you can play against Sanbonmatsu.
Beat them all.
Talk to Toki and pick Sanbonmatsu. Beat him. At the rematch you will lose and you have to find evidence of foul play.
Examine his controller on the chair.
After catching Sanbonmatsu and talking to him, the CASE IS CLOSED.