This same situation similarly happened to me when I was a toddler(?) like Eirin here. My mother had looked like she was crying about something, I became worried and reacted the same way as Eirin did in this doujin. I begged her to not cry, but ended up bawling profusely and hugging her too. I don't remember much, but I think she smiled and told me to not worry.
I couldn't help crying a bit remembering that memory of my mama. More reasons why this artist is just so extremely superb.