Kakumo Chiisaki Sekai nite

The romance manga centers on Sui Onodera, a 23-year-old who lives in an apartment. One day Sui's neighbor Kaoru Seto barges in, explaining that his dog Tino has somehow ended up on Sui's balcony. Through this meeting, Kaoru integrates himself into Sui's life.

(Source: Anime News Network)