Based on manga series "Hiru" and "Hiru Tsu" by Daisuke Imai (published from 2011 to 2013 in manga Monthly Comic @Bunch & from 2018 to 2019 in manga magazine Kurage Bunch).
The characters in the series referred to as "Hiru", or "Leech" are gatecrashers that live in a complete stranger's home while the latter is away. They sleep, eat, and relax there until the real owner returns. The group has a database of houses where they can leech off, which includes the address, where the spare key is located, and what time the owner is away.