it's always a bit difficult for me to get into a manga where the kids speak like adults......

Reading this was weird at times since it could get confusing when the children are speaking. The scene where there were playing in the sand ughh. I can't believe Masaki and Daichi are 5 years old for them to have those vocabulary.

I felt compelled to comment the same thing. It could be a product of the translation (like when Masaki says "Have a safe trip" which sounds weird from a 5-year old, but itterashai doesn't), but I'm not too sure that's the case.