A pretty lady offers her some ohagi.
That lady looks just like Tsukasa.
Tsukasa and Nasa arent surprised, since they happened to see the happy couple messing around in the park.

Nasa at least tries to engage with Yanagis problem, but Tsukasa tries a lot less.
She rightfully clocks this as the nonsense it is.
If this is the most she has to worry about, she and Taniguchi are going to beveryhappy together.

Next up, FAT NASA!
Even more frustrating, Tsukasa has the same diet but remains slim and fit.
But he has very little stamina, at least early on, enabling Tsukasa to easily overtake him.

He cant even do a chin-up at the park.
She steals his line, but he accepts it, as hes in no fit shape to dispute it!
She goads them into going on a camping trip with her, then leaves a gift behind.

Throughout their interactions Tsukasa treats the elderly woman more like a kid sister than anything else.
Of course, that happens to betrue.
So yes, Tsukasa is extremely long-lived, possibly ageless, and may even be a immortal supernatural being.

But shes also an amazing and cute-as-hell wife!She can be both!