So I tried reading How to Raise a Boring Girlfriend. Talk about a lousy manga. Couldn't even get halfway through the first volume.
Right now I'm in volume 5 of the LN for My Big Sister Lives in a Fantasy World. I really don't know WHY I keep reading it. It's not very good. Not BAD, but not good either. I mean, I can see WHY it has the standard tropes, because it's pretty obvious - basically the main character's big sister is Haruhi Suzumiya except that she WANTS supernatural adventures in her life, and she sees her little brother as the big damn hero that has them. So she inserts the tropes into his life - a growing harem, ridiculous martial arts, and so on - then watches him deal with it.
It has some vaguely interesting ideas about how EVERYONE is the main character of a story until their story collides with someone else's - then they either absorb or are absorbed by that other person's story. So Big Sister's story collides with other stories and then whoops them because she sees her little brother as invincible.