noun
being in love with an idol/actor/etc.; fan in love with an idol/actor/etc.
Slang derived from リアルに恋している (really in love). Used in fan communities to describe a fan who has romantic feelings for a celebrity, or the state of having such feelings.
あのアイドルにリアコしてるファンが多い。
There are many fans who are genuinely in love with that idol.
彼女は完全にリアコで、推しのブロマイドを集めている。
She's totally a real-love fan, collecting her favorite idol's photos.