Azusa-sou no Shokutaku

Four assassins are gathered at "Azusa Manor" as the final test of their assassination training. Their final test is to kill each other and have six months to determine who will survive. Uonari, Suzuka, Tokawa, and Mikuma, each with their own circumstances, begin living together, and start to enjoy their first experience of life in the outside world...

(Source: Natalie, translated)