When Akio and his mother move across the country to live with a mysterious acquaintance of his dead father, it's an adjustment. When they learn that the man's wife is dead and his son hasn't left the house in years, it's a shock. When the son starts letting Akio in on the rest of the family's secrets, things really start to get weird. It's going to be a long winter.
In response to Cave and Aira on the previous page, you're both pretty much right! Akio is 16, Yuu is 19 (but it's okay if he's appearing a little bit younger than that), Masanobu (Kikugawa daddy) is in his 40's and Shige (Watanabe mama) is in her mid-30s. Thank you for the comments, it's nice to know that everyone looks about the right age. xD
(If we wanna get complicated, I still don't completely understand this myself but I think it's possible that at the time this comic takes place it might have been common to use a traditional way of figuring age that's slightly different from how it's done today. But basically Akio was born in 1903, and so on.)