“Cli-Fi” means “climate change fiction”. I have discussed this term earlier here.
Now Danny Bloom (who proposed this term) asks how to say that in Japanese. And he has got a reader answer by e-mail, which he just published on his blog.
Since everyone in Japan refers to science fiction as “SF”, the logical way to proceed would be to just go for “CF”.
The alternative of transposing “Cli-Fi” into katakana would result in “Kurai-fi” (クライフィ）. I would want to stay away from that one. If the average Japanese hears ”クライ”, he will think of the Kanji”暗い”, which literally means “dark”, but means “depressing” when used in this context.
While it is true that climate change problems can be depressing, this is the last thing you want to stress when marketing a new genre of fiction.
Also, since no one in Japan uses either the alphabet or the katakana version of “Sci-Fi” ( サイフィ） in the first place, no one will recognize this pattern.
So I would recommend to just stick with “CF” for Japanese.