Characters in this game cannot level up. They can become more powerful through several ways:

1. Buy upgrade for weapon through bazaar with fragments.
2. Buy upgrade for utility skills through guild ships with dusts.
3. Gain additional quirks though visiting islands, battles or certain events.
4. Unlock different weapons, utility skills, trinkets and companions through the game.
5. Buff from Altar island or Inn and the race that you have warned about " the Ancient ". ( they will give a permanent buff for all your current party members)

Companion can only be more powerful through their quirk or the permanent buffs i just mentions.

Innes- sorry to resurrect an old thread here, but there aren't too many people posting on the forums for this game.

Would you happen to know if the permanent buffs from the story quests persist even after you use an inn's option to heal your persona and forget the good/bad stuff that happens to you?

I really don't think so, although I am not sure.

Reedo の投稿を引用：

I really don't think so, although I am not sure.

Same.