DJDAN
em... Ima just say I don't care who you pick as a Love interest here, however I don't prefer for Shizu to die tho, id prefer if she lives & becomes a ally will also throw the story off a bit as Shizu death was the main reason Hinata Sakaguchi wanted to Kill the MC so much in the manga/anime, with Shizu alive, the war might not happen, or Hinata won't get involved too much, or many just check with Shizu with whats going on.
rimaru can make his world an intairdemenshional hub at the end because if author hasn't red the web nowel then I'm not gana spoile it because rimaru did something similar and ator can go explore that world oh yeah I grave some of my thoughts on melim because u don't live over 2k year's and remain innocent it's rite n on the love interests on melim if anyone wants to check it out