@icekatze maybe because he is still inexperience on fighting another intelligence being? Because his arc enemy is said to be very powerful and have ton of fighting experience. But I agree that the author kinda brushed of this training arc and just said that its done.
If he doesn't get de-aged when he leaves, it's gonna be real weird when he gets back and is engaged/married to two girls five years younger than him. It was already weird since he's a reincarnator, but that'd take it to another level.
@Fiize MC has no backstory iirc. He just got stabbed protecting some thots and the end, NEW life. Didn't explain anything about before.
@Salfaro Yeah, I mean Idc. People be marrying much younger mates even if it's a bit much. 5 years is nothing.
I'm more like disturbed and shocked with "Your parents and I, all were summoned here. They're dead and I became an eternal God. I guess bad luck them?"