5(One Piece)

An Au where Fem Usopp instead of being sent to the island she was in canon by Kuma, for some reason she ended up in Wano in the past were she was taken in by Oden's family and trained by them.

Usopp at first was finding hard to get used to the new time and that she may never see her crew again but the people around her helped her a lot especially Izou who had found her fascinating for some unknown reason for Usopp.

Years passed and Usopp grew stronger and much closer to Izou to the point that with only a push they would be officially together but then things started to go wrong and Toki outside of sending her kids to the future she also sent Usopp back to her time while asking her to help her children and keep an eye on Izou when they met again.

Usopp thankfully ended in Sabaody so she found her crew but was overwhelmed by all the thinsg that happened in the supposed two years that she had been gone(many more years passed for Usopp so she would be twenty something when she was sent back to her time by Toki) but she dealt with that and after hearing each members' story of what they had been up to, she told them everything that happened to her and showed proof that she had not been lying about this.

Things follow mostly canon, except that Usopp had already earned her haki(if only observation or also armament is up to the writer) and that she had learned to be strong in front of any enemy, until the Wano arc(technically also the Dressrossa one since some already knew her...lets say that they hadn't connected Strawhat Usopp to their Usopp?) because Izou would immediately recognize her and some others too.

How anything else would go is up to the writer but Izou would survive and maybe he and Usopp would marry.