Otonarisan to Hajimeru Setsuyaku Seikatsu.: Denkidai no Tame ni Issho no Heya de Sugoshimasenka?

A highschooler who's living by himself - Mamiya Tetsuo is trying to save money, just like the girl next door, Yamano-san. They tried things like making their own lunch bentos and sharing a big loaf bread.... But it wasn't enough... And summer is coming, the expenses will be going up even more due to things like air-conditioning... As they wracked their brains worried about what to do, Yamano-san made a shocking proposal... "You know how we can save half the electricity bill? We should just live in the same room." Eh...? I mean it does make sense but, Yamano-san, are you serious? (Source: Kadokawa)