Teshikaga to Lake Mashu Sept 16-21

I want to see autumn colors my current plan is to skip my return flight (sept 21) and buy a new flight for around oct 1st.

I found a decent hostel deal in Teshikaga and am about to book. Is Sept 16-21 too early for leaves to start turning there. Has anyone been, is the bike riding decent? Could I ride to the lake? Are there enough places to hike within striking distance that I might consider staying longer?

My overall vibe is chill and ponder the universe, write and have long chats with mysterious travelers.

Thanks again!