From Kodansha USA:

High schooler Nozomi Koiwa wakes up and discovers she's lost her memories...and a whole lot of height. Now the size of a soda can, she flees from a feline assault into the disgusting den of Yume Okubo, a drunken shut-in NEET who's terrified of people and hasn't been outside for months. Between falling beer cans and deadly insect traps, Nozomi survives long enough to convince the airheaded Yume that she's a figment of her imagination who's come to save her from hitting rock bottom...all while investigating how she ended up funsized. But despite their differences—height, brains, and otherwise—each half of this quirky combo might just be what the other needs!