Friends Game

One day during the cold winter months, the three of them decide to go to Tetsuo's apartment after their club activities have ended.
The main character gets sent on an errand to the convenience store for snacks. While he's away, Itoha and Tetsuo begin making out.
When the main character gets back from the store, he opens the door to find the two of them having sex and quickly runs back out.
After waiting for them to finish, he enters again to find Tetsuo asleep at the kotatsu table, exhausted.
Itoha and the main character play a game. But it soon leads to them having sex
right beside the sleeping Tetsuo.