Author here! So this was the surprise! A Danmachi x MHA!
For now Izuku is 21 in the beginning since he is a pro hero.
Anyways... Enjoy to your heart's content!

Izuku 'Deku' Midoriya is a pro hero...not just any pro hero. He is the number 1 pro hero. After graduating UA, he countlessly saved people from left to right and took down villians in a snap.

However, something still remained after AFO passing. Tomura Shigaraki was the hier to his power. Ever since then... Tomura had been stealing quirks whenever he wanted. He was preparing himself for a fight of a lifetime against Deku.

They are now both standing facing each other with thier power crackling in thier bodies.

Deku: I'll just to have go all out don't I?

Tomura: I might as well show you my power as well!

Both of them were clashing fist to fist, kick to kick, brain and brawn.

Both: It feels like we are both going full power huh?

Deku: I have to go beyond for this battle!

Tomura: Let's see you try hero!

Deku: One for All... 1,000,000%...

Tomura: I won't let you!

Deku: Delaware...Detroit...

Tomura: DEKU!!!

Deku: SSSSMAAASSSHHH!!!

A enormous blast had occurred where these two launched out an attack far too destructive...

We can only see a metal respiratory mask and a hand...

Katsuki runs and tries to find his childhood friend... But stops to see him disappear into a white light...

Katsuki: DEKUUUU!

Time: Unknown
Location: Unknown
Date: Unknown

Wake up!

.....

Wake up! Izuku! Wake up!

Kami: Wake up!

Izuku: Ok! I'm up! Wait... Didn't I just die?

Kami: Of course You died... But.. I'm sending you to another world.

Izuku: Another world?

Kami: Yes. It's similar to yours except instead of heros it's adventurers.

Izuku: Sounds like a rpg game...

Kami: I guess so... You can level up by defeating monsters... Although you can only go in the dungeon by getting into a familia.

Izuku: Huh... Well do I at least still have ofa and what lvl will I be?

Kami: Oh you'll still have your power and you'll be lvl 4.

Izuku: Is lvl 4 bad or good?

Kami: Oh it's really good... Now I'll be sending you on your way...

Izuku: Thank you Kami-sama!

Kami: Goodbye Izuku...

???: You think he's gonna wake up soon Goddess Hestia?

(I do not own this art. All credit goes to the artist!)

Hestia: He should soon Bell-kun.

Bell: Though I do wonder... I've never seen those type of clothes before...

Hestia: We'll ask him once he wakes up.

Bell: Speaking of him waking up he is waking up right now!

Izuku: Oh geez my head...

Izuku grips his head with his hands but once he looks down he sees that he is 16 again.

'So I guess Kami-sama re-aged me to when I was in UA...'

Hestia: Well it seems you finally awoken huh?

Izuku: I guess so...

Bell: So what's your name?

Izuku: Oh... My name is Izuku Midoriya and yours are...?

Bell: Bell Cranel! Nice to meet you Izuku-san.

Hestia: And My name is Hestia... Or known as Goddess Hestia.

Izuku: Goddess?

Hestia: Yup! I'm a goddess... Say while we were checking your injuries while you were knocked out I saw that you were a lvl 4...

Bell: Not to mention you don't have no familia...

Izuku: Well it's just... Because of my strenght!

Both Bell and Hestia looked at each other and shrugged.

Hestia: Well since you have no familia... Will you join my familia with me and Bell?

Izuku: Sounds great!

Hestia: Great! Now let me just prick my finger and mark you as a part of the Hestia Familia.

Izuku: Sure!

Bell: This is great goddess! Now we have a bigger familia.

Hestia: That's right Bell!

Izuku: So when can I go to the dungeon?

They looked at each other again and....

Both: Soon!

Author here! Little short prologue! See ya!