Hero, Dragon, and Demon [Izuku Midoriya, Natsu Dragneel, Asta X OC]

Yuna Sakai was Izuku Midoriya's neighbor and best friend. They were inseparable. Shortly after she turned four, her quirk manifested. While playing with Izuku, she warped to a different universe named Earth-land. There she learned dimensional dragon slayer magic from the dragon Planeus and met Natsu Dragneel who was about two years older. She spent seven years in Earth-land, getting stronger with Natsu and later her Fairy Tail family. Eventually, her magic was strong enough to leave Earth-land. Before she left, she promised Natsu she'd return. But she landed in another universe instead of home. She appeared in Hage Village where she met Asta and lived with his foster family. She had very powerful spatial magic, even getting a four leaf clover grimoire. Almost five years after arriving, she told Asta she had to go home and they'd meet again. She used her spatial magic to go back to Japan and finally reunited with Izuku and her family. After seeing her for the first time in eleven years, Izuku realized just how much he loved her. Little did he know, there were two other guys that had feelings for Yuna awaiting her return.