Pages from Godzilla Couple by Shinzo Keigo, author of Green Star and some other Manga! It’s from the same compilation where I got Savior Tooth! This was used to promote Godzilla 2014! It’s official! In this story, a young couple is having sex while Godzilla is attacking!
Note, that while not explicit, this Godzilla manga has people having sex, and nipples! I would not consider it hentai, although it’s certainly erotic.
You can read the whole thing here, but be warned about the aforementioned content!: