Solo trip to Japan

Hello! 30 y/o male here. I am leaving Wednesday April 1st for Japan until April 15th. I will land in Tokyo and have 4 nights booked in Shinjuku and then my plan is to go Lake Kawaguchi-Kyoto-Osaka and then back to Tokyo for my flight home.

I love to photograph, eat, adventure, I enjoy night life, architecture and history! I am really open to any experience.

I am just looking for any advice on solo travel to Japan or recommendations on what I could do or places I could visit while there. I would also love to hear about your experiences good or bad, whatever they may be.

Thanks so much :)