Also, Yamada is 100% on the autism spectrum. He has difficulty with social communication and takes everything very literally, which leads to misunderstandings and can make him come across as being kind of mean.
@12:10 You can piece it together how old they are from information throughout the first season. But lets just say without spoilers the age gap is not big at all. Spoiler: Yamada is 18 and Akane is 20. When Akane applies for a part time job her age can be seen on the job application. And i think Yamadas age is mentioned by a classmate.
Irony is Yamada is a professional gamer with sponsors while Akane gets her living expenses paid for by her parents. So even though Yamada is a "child" he is kind of more independent than Akane is. XD
This show is so good. He is last year of HS and she in 1st year of college. If I remember correctly she is only 2 years older than him so it is no big deal.