Living as a futanari isn't easy. Few talk about the adult growth spurt. Around age 19 to 22 it's incredibly common for a sudden, spontaneous and orgasmic growth of your genitals and/or tits. Poor Kurumi had little warning but thankfully she was home.

Now she has to buy new clothes though.

(This is the true canon universe Kurumi, the one where she becomes what she is after from a trap is basically an alternate reality)