Intriguing premise. I'll be interested to see where this goes.
You have a bit of a problem with punctuation: you're missing
commas:
"Ah Mister Tanimura how good to see you."
^
"Mrs Masikawa it is with deepest sympathies that I see you."
^
The older woman waved his silken words away. "Oh stop that. I am only
dying.
^
It's the living that need your sympathies Tanimura not I. Have you found
^
Other than that, it seems well-written technically.
"So Saotome, you're trying to tell us that you fathered a child
when you were thirteen and you don't remember doing it?"
Ranma had the decency to at least blush. "I never said I
didn't remember. I just didn't understand what could happen.
I mean I was only thirteen and believe it or
not she came on to me."
I'm not entirely sure I buy this Ranma. It might've worked
better if he hadn't even understood what they were doing at
the time, or even if his "fatherhood" was some magical clone
process. Ranma is too shy with girls at the start of the series
to have had any prior experience that he understood to be such.
Kasumi and Nabiki seem IC. Akane is questionable, perhaps.
While a short burst of anger at Ranma is certainly defensible,
it might be more interesting to have her either
1) sad-and-wary (sort of like her reaction to Ukyou
in the 'Secret Sauce' story, a bit of sorrow that
Ranma will always have a shared history with Ukyou
in which she can't share) w.r.t. the boy's mother.
or
2) enthralled by the boy, and the prospect of mothering
him (but seeing him as a dress-up doll more than a
real person. Maybe dressing him very badly?).
Looking forward to more.