There's a funny error in the description of this manga:
"The 16-year old Nagisa is her sister's stepson, suddenly sent to live with Ai when his parents left for an overseas job. Wary like cats, these two loners 10 years apart in age will have to make a new life together."

On literally the written line of the first panel of the first page, it says that it is Ai's 30th birthday. That means that they are 14 years apart, not 10 years apart!