I was totally thinking about that too, and I still do sometimes... but after learning 4 languages, I'm just too tired of learning vocabulary. And this kanji system of them I'm sorry to say this but I think its just so... unfunctional. But actually learning spanish was a good choice because the spanisch yaoi fanbase and translator comunity is so big^^
I'm doing the exact same thing so we are nakamas in this I guess ╮( ̄▽ ̄)╭ I told everyone that I'm learning it because I want to watch anime without subtitles, while there is a bit truth to it, the main reason is that I want to be able to read raw yaoi manga. I'm still a beginner though so I hope I can be like you and get my N1 certification too.
So, I spent the last few years learning Japanese and eventually got my N1 "fluency" certification, and people often asked me, why did you start learning Japanese? And I give them a bunch of reasons, but to be honest, I think the #1 reason was just because I liked yaoi and could finally read raws and stuff if I just knew Japanese. So am I just a strange anomaly or are there other people out there who were driven to do strange things out of their love for yaoi?