you can read the missing first part of this chapter here:
http://wp-land.ir/ookami-he-no-yomeiri-chapter-1
It states in this chapter that the uke and seme are the same age for those worried about that
ahhh I really love this mangaka. The father's parenting was top notch, especially shown by the very last few pages which showed exactly why Koichi grew up to be such a great kid. The storytelling is so great, with just a few panels and a slight change in the character's expression you can already gather the mood and meaning of the story.
I know why everyone is upset but I just want to say most of the stories actually had a happy ending except two, so don't let that scare you away from reading the rest of the stories. One of the two with sad endings, you could tell from the start it wouldn't end well. And the last one well, that hit me like a truck too ugh ╥﹏╥
But the other stories are fine and end well!
I love this so much!! I really want a sequel of grown up Yamato and Yukio in their yakuza life, but I know that'll be angst filled and hurt me ╥﹏╥ So I'll enjoy my cute ending with pseudo-family fluffiness extras of Yamato and Yukio taking care of their child Ai (≧∀≦)