Perhaps

I was thinking it's someone from his previous work? Calling him with code name K and maybe asking him to spy on Felix for them?
╮(￣▽￣)╭

i think it isn´t important who it is... we just all know that shit is going to happen...i don´t like that...

I read spoiler from the previous comments said it was his stepfather who killed his biological father

Well that could also be a possibility though my first theory for the reason why he is hiding and from whom he is hiding to is also related to his previous work/employer so if that person is really from the previous work then it's definitely bad news (that's sad)

I thought his biological father died in an accident. This is definitely traumatic. I have never thought that an alpha could kill his own omega

Plot twists be like. Not sure 100% coz just read them from comments. We'll c what happened actually. This story give me kinda thrill. Love it, remind me of my first love (aka yaoi) viewfinder*^^*fell in love with another asami ε=ε=(ノ≧∇≦)ノ