Karl no Tensei: Transmigrated as an Assassin with a Mana Meter

Why do Gods of Transmigration love to murder their benefactors instead of asking for their help a normal way? That's how Karl got started as well. Murdered by a goddamn goddess, dumped into another world, and told to save her from her problems. You'd think gods would have their shit together, being gods and all. But apparently they do not. Karl, a teenager, who felt the inequality in his already struggling life more than ever before, finds himself transmigrated as a vice principal of a magical academy. The council accuses him of his incapability and his inexperience, believing he's not fit to lead them to the top. [ Mana meter unlocked: capacity F ] Even his cheat skill seems like a useless gimmick as Karl faces the worst students of the academy and the most difficult professors. That goddess better sends his paycheck to his parents in his old world because Karl isn't going to work for free, and if he does this job, the least she could do is pay off their debts. But then again...“I won't accept this fate handed out to me. This world might offer me the fantasies but they can't give me the warmth of my loved ones.” Would he be able to meet the Goddess and return back to his world or would he gets buried under the history of the lands that had once housed Gods and Demons alike?