Are you sure? Maybe Minori decide to play along with her mother thinking she only has one daughter. Maybe her sister is a shut-in like Waku and her mom won't acknowledge her existence.
Where does Earth's confidence come from?
I want some of that.
Edit: I love that in this manga mc is playing active role. look at demographic tab
Seinen?
What do you mean Seinen can have male mc that is not a complete doormat or an actual masochist and is very proactive???