Located a 5-minute walk from hostel DEN. Kodemmacho Station is a subway station on the Hibiya Line and you can easily go to Ueno, Akihabara, Tsukiji, Ginza and Roppongi from here without any transfers.
*Reason for recommendation
If you want to go to Shibuya, you can transfer at Ginza Station and take the Ginza Line bound for Shibuya (it'll take about 30 minutes). If you want to head over to Shinjuku, you can change lines at Akihabara Station and switch to the JR Chuo-Sobu Line bound for Mitaka (about 30 minutes away).