If you're looking for manga similar to Blue (Naoki YAMAMOTO), you might like these titles. All recommendations are made by Anime-Planet users like you!
Three ‘believers’ – two men and a woman – live on a deserted island as part of a special program. Their goal is to co-habitate and learn how to purify themselves from the outside, evil world under the teachings of Master. From day to day they remind themselves of his words and purge their vile thoughts, but soon two of them begin to discover a better, yet ‘wrong’, way to pass the time. However, Master’s teachings are absolute, and their actions won’t go unnoticed...
While Believers has a much more thorough plot than 197X, both of these works by the same mangaka do share one thing: very strong borderline H content. It doesn't kick in in Believers for awhile, but both of these involve sexual exploration and are equally as inappropriate for a young audience.
The Suzuki family runs a zoo with a difference – they themselves are the animals! With father elephant trying to maintain order by squirting everyone with water and mother giraffe attempting to keep the peace, poor decrepit old grandpa is relegated to a small hut and acts as the toilet. One day however, their family dynamic is set to change when the true nature of living by the laws of the jungle rears its ugly head…