How/Where do I make local friends in a short-term (1 month) stay in Japan?

Not sure if I should ask here or in Interpersonal Skills, but the situation arises because of travel, so I'll try here. Feel free to move it if needed.

Last year I travelled for 1 month with a couple of foreign friends I made through the internet to Japan. It was a fun, learning experience, mainly because it was my first time travelling relatively alone for such a long time and it was also my first time ever meeting those friends face to face, so we did a lot of catching up there too. Since it was our first time together and for many parts of the trip I was the most fluent in Japanese, we mainly did everything together.

I'm back in my home country, but the group liked it so we will probably repeat the trip next year. This time around though, I'll probably try to enjoy certain parts of the trip getting to know the locals more instead of only sticking to our group. I can get around speaking conversational Japanese (Besides English and Spanish), so it would probably be fun if I could have a few local friends.

I would not consider myself an outgoing person but I've been putting effort into changing that lately, so I thought this would be a good opportunity to both improve my communication skills and get something new out of travelling. This is because I've spent most of my life studying and working, so the network of people I've made is centered around long-term group activities like that. I don't have much experience making friends out of random encounter. That said, I found it a little bit difficult to find places to meet local people in Japan in a short-term stay. Most foreign people I know that live there say they make friends by joining a club, participating in certain group events, at work, etc. but that's a bit difficult due to time. I come from a Latin American culture if that is of any relevance.

How can I make local friends in Japan? Which places are good for meeting locals? I've read about Roppongi for example being a hotspot for foreigners, but I haven't really tried nightlife like that alone before. Are cafes good places to start up a conversation? How do I even do this without coming along as awkward or dangerous? Are there any kind of events specifically aimed at people trying to make friends?

I'll mostly be around Tokyo, but I'll be travelling to other parts of the country as well, so any general suggestion is welcome.