The Accidental Contract (System School, Book 3) by Kos Play
Listen to a sample:
Melvin is lost when Kalli returns to Gaia.
After pushing his friends away, he turns to his newfound skills as a healer for some much-needed solace. Paired with an unlikely partner in crime, Melvin must once again rise to the occasion when an ominous message comes from another world. Kalli is dying.
Join Melvin and his friends as they explore another world in an effort to save Kalli and get out of The Accidental Contract.
Book 3 of this lighthearted and often hilarious LitRPG Series about how two kids from different worlds grow into their own while surviving things like classes, bullies, vampires, and worse.