Doona!

Doo Na, a member of the girl group Dream Sweet, suddenly left the group one day and ends up living in the same share house as Won Jun, a college student. Doo Na mistakes him for being her sasaeng fan, and Won Jun does not know who she is. They become curious about each other.
(Source: Korean = Netflix Korea || Translation = MDL)
~~ Adapted from the webtoon "The Girl Downstairs" (이두나!) by Min Song Ah (민송아).