Hapitora Gaiden Aina no Shinkon Nikki

Aina, the island’s top ace Sylphid, continues her daily routine of showering the protagonist with affection.
With an innocent “I’m your mom and big sister substitute, after all♪,” she clings to him, sneaking into his bed or showing up in nothing but a button-up shirt—leaving him both thrilled and flustered.
To make matters more complicated, the other girls are away on a trip, leaving just Aina and the protagonist alone in the house…!?
Seizing the moment, the protagonist makes a bold move—he kisses her and proposes!!!
But… Aina, who’s usually so forward, suddenly turns shy and fidgety!? After all that casual skin contact, why now?
“Because… all that before was just family affection,” she explains.
And so begins the story of Aina, the big sister figure, and their sweet, awkward newlywed life together♪

[Translated from the official website]