After clearing Bad-Mouth Sugoroku, Yuichi and Tenji find themselves trapped in a dark cave for three days. During their isolation, Tenji makes the shocking revelation that he had already experienced a Tomodachi Game in the past. Meanwhile, a team of new opponents lies in wait outside, anxious to challenge the two partners to a grueling third game.

The third game, Friendly Hide-and-Seek, begins. Rival Group K, bolstered by an apparent 'genius' strategist, proceeds with a clear numerical advantage. Eager to regain Yuichi's trust, Tenji volunteers to be Group C's hider, but the couple's plans are strained by the addition of a new female teammate, Mizuse Maria. Yuichi confidently tells Tenji to "just trust me and wait," but then doesn't return for days...

Yuichi, who hasn’t left the starting point in the two days since the game began, suddenly announces his desire to switch to Group K. The Group K members, puzzled by Yuichi’s apparent intention to abandon his hiding teammate, ask their Captain to decide whether or not to let Yuichi in. Meanwhile, Tenji, who has stayed in hiding and trusted Yuichi all along, is finally reaching his physical breaking point.

Finally able to shake his Group K guards, Yuichi succeeds in delivering food to Tenji. After being pushed off the cliff by Yuichi, Maria slowly gets closer to her saviors Hyakutaro and Chisato, but that too is a trap set by Yuichi to destroy the friendships in Group K.

With "true genius" Kei controlling things from the shadows, Group K succeeds in finding Tenji. Facing the "worst thing that could have happened," Tenji makes a phone call to a certain individual. The third game, Friendly Hide-and-Seek, then reaches its conclusion. While the two groups struggled to outwit each other, Shiho, Shibe, and Yutori, who had been temporarily released for the third game, returned to school only to be met with cold stares from their classmates.