This is a great place for 1 (or 2 who really get along) to sleep after exploring the city all day, but it's really too small for anything else. The space is clean and the host provided some nice little touches of style and friendliness.
Okubo itself is Koreatown. The building is off an alley crammed with izakayas and Korean restaurants that get seriously busy in the evening. Shinjuku is also a short walk south, with a Don Quixote on the way. Don't even bother with the pocket-sized shower in the room; Mannenyu Onsen in the next alley over is very friendly to foreigners.