
Wtf I'm lost
1. 5yrs later oh now he's paying attention to him trying to act everything is okay
2. TF you mean he stole your powers dude you just fainted thats all
3.Who was the grey hair guy and he did called him Sia

Answer to your questions here
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1- only reason he come back acting all touchy with uke cuz he wanted to make uke regain his memories ask to remove imprinting and after that uke will manifest as s rank guide instead of f , seme is aware there is something wrong with this whole situation he is himself s rank esper why uke isn't S rank guide but his plan changed as he gets to know uke.
2- seme is dramatic af he is literally hippo
3- that guy is uncle of seme he has issues with seme and I guess abandoned by family line so he kinda own uke and knew him since he was kid he is mind manipulator so he is the one who make uke believe he is F rank guide not S rank .

Wait I had to stop reading because wtf is a Cakeverse this is the first time I hear about this because it used to AlphaxOmega for some time then years later AlphaxAlpha Alphaxbeta then BetaXOmega what's next OmegaXOmega then BetaxBeta
And another thing freaking DOMXSUB like I just find out about it years ago but still this one is a bit fresh
Damn this is getting intense