Mesu Ochi! Ore no Netori-bou de Midara ni Aegu Senpai & Kouhai Tsuma ~Mucchiri Nikuatsu no Kyonyuu Tsuma-tachi to no Hamehame Love Life~

The main character is an ordinary salaryman. He had feelings for Mai Hidaka, a senior coworker who served as his mentor during his trainee period. However, she got married after his training ended, so he gave up on her. Though his senior seemed to have been living a happily married life, he recently noticed she'd been sighing a lot more. While trying to cheer her up and offer advice, he began to recall his past feelings for her. One day, on the way home from a department drinking party, he witnesses Mai's husband with a female coworker from the same company as him. "No way..." As he's agonizing over this, he coincidentally reunites with his junior, Satone Shirakawa... [Translated from DLsite]