Can someone spoil me, if she at the end choose to stay 15yo, does that mean there's no ML?...

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From the spoilers I read, he waits until she's legal to propose

But he is an old man by then. （￣へ￣） they shouldn't have put a ml at all.

I agree, or at least make him a little younger than her form the beginning. But I think in the end they'd only have about a 5 year age gap so