You and Togami were secretly dating. He didn't want it to be known he was dating a commoner, especially to the other students in Hope's Peak.

Bomb Scene:

Yasuhiro was panicking, trying his hardest not to move a muscle as Togami told him 'That bomb should go off at the slightest vibration.', everyone around literally shaking in fear. "Oh Dear, I'm sorry. Did I forget to mention I already deactivated the sensor?" Togami suddenly spoke in a mocking and sarcastic tone. Everyone looked relieved,