Its not that rare these days, in fact id sag its common in 2020 era manga. Maybe its the spirit of Abe trying to revive the birthrate, but a lot of the ones im reading now, ranging from this one to "my boss is scary" to "my divorced crybaby neighbor" involve an adult, reasonably well put together man making friends with a similarly mature woman, either a neighbor or coworker, deepening their relationship, and then boning for fanbox content before the first quarter or third of the series is through.