Would you?

You were teleported in the world of re zero and given the task of helping one of these girls with their problems.

You replace Subaru.

Zarestia. (Best girl) Help her get her light sphere back. (Rbd?) (Sloth if)

Emilia. Help her get her insignia back. (Arc 1) (rbd)

Rem. Get 1 child out of the forest. (you are deep inside forest) (Arc 2) (rbd)

Elsa. Help her kill everyone in the trap mansion (that includes Garfield) (arc 4) (no rbd) (and no Subaru cus he doesn't exist, tho his trap still exists)

Frederica. Help Garfield get over his trauma and make him leave the sanctuary. (Arc 4)

Anastasia. Convince her and Crusch about the location of the white whale and fight it. (Rbd) (arc 3)

Crusch. Fight the white whale and find a way to get Crusch away from greed and gluttony. (Rbd) (arc 3)

Priscilla. You replace liliana. (No rbd) (arc 5)

Reward would be the girls falling in love with you.

Of course your still stuck in the world of re zero and can change the future events after you finish ur task. Note you spawn in the start of the arcs.