Sure! I'll go with what my friends recommended as well, since I haven't travelled to all of the locations I want to go yet. Tōkyō is of course pretty bustling, and has a lot. Kyōto, Ōsaka, and Nara (i.e. the Kansai region) are all close to one another, so it's a good area to visit and sightsee. Although, it can get incredibly crowded with tourists. Other places people mention they like are Sapporo in Hokkaidō, and maybe Fukuoka in Kyūshū. Also, what the other commenter mentioned is good advice. Feel free to PM me if you have any other questions.