Shizuku-san wa Ore no Omoibito

In a certain apartment lives Mamoru, a university student, and living right next door is his neighbor, an office lady named Shizuku, and her daughter, Mizuki.

They are very close — to the point of eating meals together — but Mamoru and Shizuku can't quite close the final gap. Out of concern, Mizuki lends them her support by leaving the two of them alone on Christmas Eve to spend one night by themselves... which turns into a lovey-dovey vanilla story!

(Source: Melonbooks, translated)