Sweet Moratorium.

Kashiwagi Kokoro is a university student. He enjoys his campus life and has begun dating Kamijo Sayo. One day, his ex-girlfriend Omori Ringo, who is the one that decided to end their relationship, visits his home and begins to live there. Kashiwagi Kokoro doesn't tell his new girlfriend Kamijo Sayo about Omori Ringo moving in with him. (Source: AsianWiki) ~~ Adapted from the manga series "Sweet Moratorium" (スイートモラトリアム) by Tama Izumi (たまいずみ).