Same level of weirdness - what sums up both movies well. Otakus might have higher quality and be more theatrical while Quiet Room has a story to tell.

In both movies there are dysfunctional teenage girls that causes problems to their surroundings. Both are rather slow paced and and not an easy watch.
However, there is no romance in Gaichu and it's set around a school.

Similar crime stories, Tanaka Tetsushi in both. Yami no Bansosha is investigation as the main issue while in Tsumi to Batsu it's, still there is an outcast in the foreground.

Both are psychological, but Tsumi to Batsu in a more dark and probably less "human" way. They deal with opposite issues (celebrity vs. troubled youth) but there's a lot of conspiracy in both dramas. Plus the cast: Tanaka Tetsushi plays a kind of similar role, there's also Mizukawa Asami in both.

ok, it's not a direct recommendation, the movies differ, notably in the case of music - Fish Story is about music, See You is definitely not. But there are some links: time span, Hamada's similar role, general climax, different stories involved.