This is barely related to the main story, Izuku will only learn some new techniques that he'll use in the main story. He'll not gain anything from these spin-offs, just techniques on how to use his original power. You can skip this chapter and every other chapter that has the word "spin-off" in the title. The first spin-off series is about Izuku in Genshin Impact because it's my favorite game
Izuku Midoriya just woke up on a beach with his hero costume for some reason, he stands up and looks around wondering where he is until he heard frantic water splashing noises, he looks at where the sound came from and sees a small white humanoid creature drowning in the ocean, Izuku's hero instincts kicked in, he flew and caught the creature like a hawk catching fish, as they landed the creature screamed out.
creature: Ah! please don't eat- *It opens its eyes* huh, who are you?
Izuku: I'm Izuku Midoriya, what happened to you back there
Creature: Well I was trying to catch fish but I almost drowned
Izuku: Are you alright? Are you hurt anywhere?
Creature: I'm fine.
Izuku: That's good. by the way, What's your name, and where am I?
Paimon: My name is Paimon, and you are at Starsnatch Cliff
Izuku: Starsnatch Cliff, doesn't ring a bell...hmm I wonder where I am
Paimon: Do you know anything about Teyvat?
Izuku: No. That's not a country I'm familiar with
Paimon: What's a country?
Izuku: Wait, you don't know what a country is? A country is a large landmass with a defined border and recognition from other places to be called a country.
Paimon: So a country is like Liyue or Mondstadt, you're making up weird terms for things. Anyway, where did you come from?
Izuku: I have a theory, I think I'm from an alternate dimension. Do you guys have things like quirks?
Paimon: What are quirks?
Izuku: Hmm, it seems like I really am in an alternate dimension.
Paimon: Wait what?
Izuku: well, in my universe we have things called quirks, quirks are superpowers 80% of the population had.
Paimon: Do you have a quirk?
Izuku: Yes I do, it's why I have these wings, I also have abilities other than flying
Paimon: Can you tell me what they are? Does any of them involve food?!
Izuku: I'll explain, you should probably sit down, this is going to be a long one *Izuku then explains all of his powers up to the bell of truth*
Paimon: So let me get this straight? You have the powers of controlling different phenomena you call your graces like the grace of tornado or grace of ocean?
Izuku: Yep, that is correct.
Paimon: You also have the ability to make anyone who holds hatred in their heart unable to afflict harm on anyone else and petrify anyone who lies or goes back on their word into stone
Izuku: That's also correct.
Paimon: You can also summon dark swords, reflect physical attacks at opponents at more than twice the amount of damage, create a ball of light that can destroy every inanimate object around it in a large area and make your opponents' pain and suffering into pleasure but make them unconscious while also being able to cancel illusions
