Zenless Zone Zero's Re-Traveler

The author is inexperienced, so please point out anything that seems unreasonable. The author also doesn't fully understand some characters yet, so please feel free to point out any out-of-character moments, and I'll revise them all.

Also, the protagonist is a guy. He won't go overboard protecting the Phaethon siblings, and some of the tragic moments will be changed.

(Male protagonist, physical combat, somewhat overpowered but still takes a few hits.)