He's the senpai that mayama confessed to during school years. That senpai outed him to the whole club, so mayama quit the club. Then they met again because they're in the same company. But the senpai has been nasty and harassing the manager's ex-wife and mayama testified as witness. Then the senpai did a smear campaign that ended with mayama got transferred to the manager's place.

can someone help me understand what happened with mayama and his old co worker that got him in trouble? also i love midorikawa, shes so caring