Reader-added tags include "Take a chance and make a break", "Reason for concern (in a sense)", and "Vague and fuzzy".

So if he's the 52 year old child....

Mizuki said:

As for the children's room, since it was confirmed we couldn't expect to have kids, it's become a toy room for a 52-year-old child. :-)

What?

Mizuki said:

As for the children's room, since it was confirmed we couldn't expect to have kids, it's become a toy room for a 52-year-old child. :-)

Etnaz said:

What?

Now you mention it... I always thought they don't have kids because they couldn't afford it.
Could it be it was actually due to physical issue?

Etnaz said:

What?

There's some questions and speculation among the Pixiv commenters about the meaning behind that statement, but Mizuki-san hasn't said anything additional about it.

One commenter figures it's probably an age thing, implying that even if there were no medical reasons during their younger days, their lifestyles simply didn't allow for having kids, and now it'd just be too much at their age. As noted, though, it's all speculation.