
Not sure which chapter you are referring to, but in general age in Japan is a bit complicated because it also takes in consideration of the birth date. A person doesn’t gain a year of age until after their birthday. For example, if I had been born in 1 Dec 2000 then in Japan I would be 18 years old right now, but 19 years old in most of the rest of the world.

Haha, you didn't need to do the math for his current age..it's already been said he is 36 yrs old on chapter 4.
I also don't think he lied about his age. i think he messed up his correct age because he doesn't really know how old he is...like he is lonely as heck and stopped counting his birthdays when ryou disappeared back then. he also has no one to celebrate it with so he doesn't care about it.
but if author san really intended to make him lie about his age then thats really funny.
Ok, so... It was 1987 when he was 14. Now when he's, like he says, 37, is 2009. So, 1987-14=1973 (this is the year when he was born). That means that his current age is 36. First he said he's 35, and then he said he's 37. He was lying for his age 2 times... I've never had to do math for a yaoi manga.. What the hell... I spend like 5-10 minutes truing to figure it out... There's something wrong with me XD