I picked this one off based off how cute the boys are. The art style is SUPER cute!! I love it.
There's a bit of an age gap where the older boy is at least 3 years older and the younger boy is a minor. Nothing more than kissing happens while the younger one is still a minor.
The characters and dynamic were not particularly interesting. The older boy was disowned for being gay and leaving his arranged fiancee at the altar and the younger boy is an orphan.
Despite the rating of only 17+, the boys are doing handjobs and butt fucking. It caught me by surprise, so here's your warning since the publisher won't warn you.
Umibe no Etranger is technically a one shot which was continued into a series with Harukaze no Etranger. As cute as the boys are, I won't be continuing it. I enjoyed Qualia Under the Snow from the same mangaka though! Their dynamic was much more interesting, so check that one out instead.