Birthday present wholesomeness.
We almost had one chapter just full of wholesome good vibes until that last part. Can't the conflict wait just a little bit more? I guess this is his grandpa's scheme in motion. We do have to come back to that eventually, now that his birthday moment has passed, but man they just can't catch a break.
I don't know how Eiji will fight back against his mother's family's harassment of them (short of somehow taking over as the grandson), but if Aoi knew she'd probably enlist her own family's resources to help. At least her family supports them, so it's not truly a bleak "them against the world" situation here.