Rui and Tsukasa are very great friends who made a strong bond with each other, but Rui, started to gain feelings for Tsukasa. But he wasn't sure about it and mostly pushed the feelings away, but one day Rui fell in love with Tsukasa and became a complete boyfailure if Tsukasa gets too close to Rui he dies, when he speaks to Tsukasa he can't even formulate a sentence etc.

While Tsukasa, well, he doesn't understand what is happening and confused by Ruis change in his behavior it was wierd to Tsukasa and new because he never saw Rui act like that