Well, the bartender helps with the story quests... What to do next.
And to find the second piece of underwear you need to go without parasites.
And it's extremely important to read the dialogues. There are usually hints there.
i might had realize i break the game since i got rid of the the oarasite by the teleport to one of the demon king general cutseen in which the parasite dissapear so i dont know if that meant to happen ;-;
This is one way, since the Demon King has isolated, if possible, parts of the distorted worlds.
