Gotta go along with most of the commenters on this thread.
1. The sister is B.S. None of this family is his family. It's not his world, he is 300+ not 18 and he likely buried everyone a long time ago. Not to mention the "sister" in this world is a waste of flesh
2. Who cares what family she winds up in ? Per #1 she is good for nothing they should be looking to pawn her off
3. It's been a complete distraction from him fixing his real problems and what's more it's the kind of thing that attracts attention he doesn't need.
4. The last few arcs have been made to appeal to people that want to see the MC be someone's BIATCH. Having the Granny be credible ???
Saved by the loli, was interesting but not well done. Reading it, it really felt like it was pulled out of nowhere and was just the writers not properly developing their story.