Kimi to Honori, Hatatose no Aida de.

First-class architect Ikura Kento is in his forties, living a stable, settled life after growing tired of new romances and friendships. One day, at a major architecture event, he unexpectedly reunites with his high school classmate and former boyfriend, Ishizaki Atsushi…?! A rekindled love story between a poker-faced lumberman and a cheerful, courageous first-class architect. (Source: Ichijinsha, machine translated)