Yeah, I just remembered. Shiouji's age has been mentioned twice - once in volume 12, when it's said he was fourteen when he first met Umi, and the second time in volume 16, when Kabapu? (I don't think Tenmangu was that neglectful a father) says that when he last saw Shiouji, he was only three years old, which would suggest that there'd been at least a year when Kabapu'd last met baby Shiouji. Now, this exchange happened 22? years ago (Kabapu first met Tenmangu "about 30 years ago". Tenmangu disappeared 20 years ago. The discussion happened when the Ropponmatsu prototype had been completed, which was said to have taken eight years. Hence - assuming the clock started ticking immediately after Tenmangu met Kabapu - 22 years), so Shiouji'd been four back then, which is where I got my present-day 26. How's that for "easy calculations"?
This would also make Umi 6 when she first met Shiouji, which - like her present-day age of 18 - I also think was mentioned somewhere, perhaps as canon a source as the Oubliette or back cover.
Going on another limb here, Watanabe and co. are at most 23 or so. They're all college graduates, which usually happens in Japan at the age of 21, and I don't think they could have survived being unemployed for several years, and none of them apparently had a job prior to work in the City Environmental Security Administration.
BUT THEN AGAIN. I'm wondering if someone has actual facts, or even alternative theories.
