I had a friend who played RPG's with this mindset. He would always over-level his characters before he went into a harder zone and would grind trash mobs until he felt comfortable moving on.
I get the feeling that Seiya is only prepared to enter that world now.
But then he will start preparing for his first excursion:
Slaying a slime or a goblin or whatever weakest monster there is in the next forest.
Preparation time: 1 month (at least!)
???
Also in case he is supposed to register as an adventurer you need to add 2 weeks to that preparation time.
1 week preparation to adjust to that world's society in both terms of social/political and technological status.
1 week preparation to then enter the adventurers guild and register there.
Btw. there is one GIANT issue that I noticed with his status:
There is no auto-translation or language adaption skill in his status.
So how is he gonna communicate in that other world?
Sure, it took a month to explain to the Martian, but it's her own fault for pulling in J'onn J'onzz before he got into Manhunter-ing. Worked out okay in the end.