Canary and Swallow makes great MystiAlice doujins but the cuteness level here just makes me stray away from it. Then again, I am an open-minded person so I don't have much OTP and stuff like that.
In German, homosexuals are often referred to as "someone from the other shore/riverside" (vom anderen Ufer), and when I read this, I actually thought of that idiom as in "crossed over to the other riverside".
Such an idiom doesn't exist in English or Japanese, right?
What you describe reminds me of "coming out of the closet", but as for that specific idiom, no, I don't believe it does exist in English. But I wouldn't know about Japan.