I'm looking for manga where people sign up to be adventurers. You know, like they accept missions or quests and then they do them.
Any reccomendations?
Also, it would be great if magic was included.

Obsessed with reincarnation
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Key to the Stars

Among the isekai novels/manga that is a fairly common occurence. Of the top of my head Wortenia Senki, The New Gate and Nidoume no Jinsei wo Isekai de (My current favorites).

Also ,the ones that are essentially a game definitely fits, Toaru Ossan no VRMMO Katsudouki, The Legendary Moonlight Sculptor and Only Sense Online.
Now that I think about it The New Gate is also about a game...ish... Huh, I keep forgetting that.

~4400 manga completed
~1700 ongoing...

Fairy tail