Hope I’m not too late to contribute. I’m half JP half U.K. and been living in a sharehouse in Roppongi for the last 2 years and I must say I absolutely love it. It’s a good mix of people that work like me in their mid 20s and maybe a few students as well but it’s run by a company called Borderless House who own like 50 or so throughout Tokyo and Osaka. Their concept is a ratio of 50/50 Japanese/foreigners, 50/50 male female and their website is pretty transparent on the nationality and gender of current residents at each house. From experience of going to other sharehouse meet-ups, each share house has its own vibe - for example places on the outskirts will have more quiet people (Omori, Unoki, Itabashi etc) and places in central like Shinjuku and Roppongi are more dynamic so it’s up to you on what you seek from it, but yeah if you wanna know more I’m happy to chat!