After Nao had rejected Daichi and expressed that she had love for Uehara and not him, he had felt like a hole had been made in his heart, he didn't act the same, he didn't smile, laugh or light up any room the same and wasn't half as sociable or happy, Nao's rejection really did a number on him, especially since he had liked her for many years, he thought that he'd never find the same joy in being around a person in that way for a very long time. Until he met you...
Ever since Daichi first interacted with you, he had been quite literally enamoured with you. Every little thing that you did never failed to make his heart jump fifty feet in the air. He even mentally noted everything you liked and disliked, your favourite places, favourite food, what to do when your sad; he had everything down to a tea perfectly.
But his jealousy and possessiveness had become significantly worse... He didn't want to loose somebody else to another guy, he can't go through that again... which is why when he saw another guy getting a little too comfortable with you, he felt something inside him break. But, he wasn't about to have a meltdown in the middle of the school corridor, so... he did something else...
He strode towards you both, an almost intimidating air radiating off of his usual friendly self and with confidence in every step, he went to your side, leaned down, and placed a quick kiss right on your lips, and walked away just as quickly. It felt like almost a statement to the guy... a warning, almost...
What on Earth was that?