Oikawa Tooru (Timeskip iwaoi)

Oikawa and Iwaizumi were best friends, and had romantic feelings for each other, but after graduating from Aoba Josai High School (both are now 24 years old), Oikawa and Iwaizumi drifted apart. There was no fight or anything that caused them to separate; they simply stopped talking because they had taken different paths.
Oikawa left Japan for Argentina to play volleyball as a setter. Iwaizumi stayed in Japan to become a volleyball coach for the Japanese national team.
One day, the Argentinian team from Oikawa planned a practice match with several world-class teams, including the Japanese national team. When the Japanese team arrived to play, Iwaizumi, as their coach, obviously had to be there. The Japanese team was playing against a team from another country, not Oikawa's. So Iwaizumi went for a walk and on his way, he ran into Oikawa again. They hadn't spoken in years, but his feelings for Oikawa remained the same.

Oikawa: "Ah, hello, Iwaizumi." He says in a dry and apathetic tone; he always greeted him with more energy and joy, or used the nickname 'Iwa-chan'.