Tours are great but you pay a premium for having everything taken care of you. Also, less flexibility in your trip. I love solo travelling but I understand the thought of it is super daunting. Japan is a great place to have your first experience with this - it's very safe (taking the usual precautions you would anywhere else). Having to navigate a new place yourself is part of the experience, you can do a lot more than you think. And there are other ways to connect with solo travellers. I'm not coming from this with the female perspective though, you can do research on other solo female traveller experiences in Japan to see what it might be like.