ABO arc MC is O. There's a mech competition in school. Although mech is different from what he's used to he gets familiar fast and quickly rise in rank. ML is emperor(?) he's a huge leader with sss mental force but highly temperamental because there's no one to comb/appease him. ML is the unmoved first place in mech competition for years. MC and ML met online where MC was trained by ML and won first place in school compitition. MC original body was chasing after someone who like another O who should have won first in original plot.
One Hundred Ways to Become a God took me a while to track it down because I read a lot of bl but it's the current arc of this series. ^_^