That 0.0001% possibility

I'm sorry but I can't help but think of the possibility if Iroha had successfully persuaded Kaguya not to return from the moon, and run away together, then there wouldn't be Yachiyo or she would have vanished. I wonder, if that would still be "considered" a happy ending for Kaguya and Iroha? I'm thinking for Iroha it wouldn't be because Yachiyo disappeared and the VR world Tsukuyomi would seize to function. And seeing this, this would probably make Kaguya really sad too.

This is what I think but I want to hear some thoughts from you all....