It seems like you are afraid to leave your comfort zone. There's nothing necessarily wrong with that, but in the end you have to ask yourself "Is this life fulfilling?"
As I was in a similar situation, this is how I approached/viewed it.
Even though there are some petty (and some not-so-petty) annoyances, living in Japan is pretty easy. I got to a point however where I just was not progressing. Professionally, I had become a full-time university instructor but even that still merely felt like a job, not a career. As far as my personal life goes, I had made a lot of acquaintances but developed very few real friendships. I had also made some girlfriends here and there but it was really hard to envision settling down with most of them. All things considered, it just felt like I was killing time.
It wasn't an easy decision to leave. Heck, as you know I flip-flopped on it more times than I care to admit. ^^; Still, long story short: After all those years (and flip-flops) I finally felt like I was done with Japan. Not everyone has to feel that way of course. Many foreigners settle down in Japan and lead perfectly normal, productive lives.
You mentioned being "afraid of the high crime rate and the large amount of foreigners and teenager delinquents in Germany". Are those things really so hard to deal with? Outside of Japan, crime is just a fact of life. You have to know how to take care of yourself. Dealing with foreigners? Ummm... you are a foreigner in Japan. I don't know what you're trying to say with that one. Teenager delinquents? Again, similar to crime, you just have to know how to take care of yourself. Sorry if I sound like a jerk but being afraid of these things makes me just want to say "Grow up!"
You also mentioned feeling horrible and desperate in Germany. I don't know what that was all about. There are some things in life and the world that one cannot control. If some the types of things that made you feel horrible and desperate would resurface upon your return to Germany then I wouldn't want to go back there either - but that doesn't necessarily mean stay in Japan.
Then of course, the big question what to do if you leave. Well, what can you do? What do you want to do? Ideally, you would find something that answers both. Anyway, it looks like some more soul-searching is in order for you to find out what is truly best for you, and only you can discover the answer to that. Good luck!
This is just my opinion but...
As I was in a similar situation, this is how I approached/viewed it.
Even though there are some petty (and some not-so-petty) annoyances, living in Japan is pretty easy. I got to a point however where I just was not progressing. Professionally, I had become a full-time university instructor but even that still merely felt like a job, not a career. As far as my personal life goes, I had made a lot of acquaintances but developed very few real friendships. I had also made some girlfriends here and there but it was really hard to envision settling down with most of them. All things considered, it just felt like I was killing time.
It wasn't an easy decision to leave. Heck, as you know I flip-flopped on it more times than I care to admit. ^^; Still, long story short: After all those years (and flip-flops) I finally felt like I was done with Japan. Not everyone has to feel that way of course. Many foreigners settle down in Japan and lead perfectly normal, productive lives.
You mentioned being "afraid of the high crime rate and the large amount of foreigners and teenager delinquents in Germany". Are those things really so hard to deal with? Outside of Japan, crime is just a fact of life. You have to know how to take care of yourself. Dealing with foreigners? Ummm... you are a foreigner in Japan. I don't know what you're trying to say with that one. Teenager delinquents? Again, similar to crime, you just have to know how to take care of yourself. Sorry if I sound like a jerk but being afraid of these things makes me just want to say "Grow up!"
You also mentioned feeling horrible and desperate in Germany. I don't know what that was all about. There are some things in life and the world that one cannot control. If some the types of things that made you feel horrible and desperate would resurface upon your return to Germany then I wouldn't want to go back there either - but that doesn't necessarily mean stay in Japan.
Then of course, the big question what to do if you leave. Well, what can you do? What do you want to do? Ideally, you would find something that answers both. Anyway, it looks like some more soul-searching is in order for you to find out what is truly best for you, and only you can discover the answer to that. Good luck!