Masato knows something's up when Jinguji walks into their room without a sound, not even a smark remark towards him about something or other, and just sits on his bed, watching the heir with a look he can't read. The staring continues for a few minutes until Masato breaks contact and continues sewing a tear in the clothes Otoya'd given him to repair, knowing he was handy with a needle. He's so focused, he doesn't realize he's been asked a question until Jinguji's beside him whispering it in his ear.
"I didn't know you were so hard of hearing, Hijirikawa, but I'll ask again: How long can you hold out?"
And he knows exactly what the other's talking about, flushing slightly and doing the best he can to ignore the breath tickling his ear.
"Longer than you, Jinguji." It's more embarrassing outloud than it is in his head, and his roommate laughs with a cocky smile on his lips. And he kisses him - just a short one, full of challenge and confidence, and Masato restrains himself long enough to not kiss him back to show him just how long he could last.
"For someone who hasn't even touched themselves, you're confident, Hijirikawa. Are you really willing to try, or should I accept your forfeit now?"
Masato frowns slightly, his eyes narrowing at the too-obvious challenge, and looks back down at the abandoned project. "You're childish, Jinguji, and it would do you good to fix that before others remark on it."
"I figured you would avoid losing if you could." Jinguji stands and Masato purses his lips, not wanting to back down but not wanting to lose either. He pulls the other down without a second thought and presses their lips together, fierce and determined, and he can feel the knowing chuckle and look from his roommate as arms wrap tightly around him despite having closed his eyes.