Aaaaand Hina-chan saves the day!
Rei did not realise that taking serious his proposal right now would not only be a monstruous pression over the girl that is mentally still a child, but would also bring lots of problems to her in school for example, since they both are togheter there.
The bullying arc would come back like a trainwreck.
And the mad man was thinking in giving an engagment ring to her uses in the school! HAHAHAHA
Thankfully the author was able to came with this "Dream Ex Machina" to avoid all that.