At least in my opinion, Ida is still a really mysterious guy... I'd like to know more about his past, and am hoping this sequel contains that?

I personally never really cared much for the romantic development in this story (Ida just really isnt the type...) So I preferred his previous partner, "Hachimaki"... He had a family, and was a more stable character than some new stereotypically idealistic woman.

An issue I had with Jiraishin was that I was never sure how fast time was passing... How old is he, anyway?

No idea how old he is, but they might have said it at some point. The only real hints I saw about how the time was passing were the ages of a couple characters.
1- The evil little girl (Aya or something) from one of the earlier volumes, who is 9 in one of the earlier volumes and 12 in one of the later ones.
2- Ida's first partner's kid is born in one of the earlier volumes and is a toddler later.

"It is those who know little, and not those who know much, who so positively assert that this or that problem will never be solved by science."

Iida is rather timeless =D I never recall any age being mentioned in the original. I'm reading through Diablo v1 right now, and one of the main chars is Kioke Aya (who was age nine in volume 7 of Jiraishin). She's all grown up now, looks like 20-something.

Some serious time has passed since Jiraishin and Diablo, and Iida is hardly unaffected by it in the sequel. Anyway, you'll see a scanlation come out soon if you don't have Diablo, so I won't spoil anything... 🙄

Oh! I can't wait! I tend to like manga like this, even though it makes me cry...

..... What happened to his EYES?

considering his age: he met azusa when she was 19. kyouya should be a rookie or something, early 20s. when she was 24 she killed the dude and died after starving herself in prison (chapter 1 - blue sea&red rose). in chapter 10 - inducing, the date is jan 1994. this means that he met azusa (if takahashi's timeline is continuous) in 1989 or earlier. first chapter of jiraishin diablo is in nov 2008. he should be about 40

I want to know why he was so affected by that MAO drug in Jiraishin... Do you think that will ever be explained, that momentary single frame flashback?

.... 40.... he's old now 🙁
I'm just gonna keep thinking maybe he's 37 or something... it doesn't have to be 5 years, does it? I don't feel like searching for the reference....

Gotta say, I'm pissed Takahashi killed off Narita... and that doctor looks so old now... It's just, if he's 40, he's not gonna be young enough to go hunting his criminals no matter where they go, right?