Mitsubishi Ichigokan Museum is a cultural site in Chiyoda Ku, Tokyo. 5 YouTube travel vloggers — including がるザラシちゃんねる【ガルちゃん有益まとめ】 — have covered it across 8 clips.
A museum with a small garden, located a short walk from Tokyo Station.
“That is the "Mitsubishi Ichigokan" Museum.”