Grand Blue 碧蓝之海Among the seaside town of Izu’s ocean waves and rays of shining sun, Iori Kitahara is just beginning his freshman year at Izu University. As he moves into his uncle’s scuba diving shop, Grand Blue, he eagerly anticipates his dream college life, filled with beautiful girls and good friends.
But things don’t exactly go according to plan. Upon entering the shop, he encounters a group of rowdy, naked upperclassmen, who immediately coerce him into participating in their alcoholic activities. Though unwilling at first, Iori quickly gives in and becomes the heart and soul of the party. Unfortunately, this earns him the scorn of his cousin, Chisa Kotegawa, who walks in at precisely the wrong time. Undeterred, Iori still vows to realize his ideal college life, but will things go according to plan this time, or will his situation take yet another dive?
北原伊织升入大学后，开始寄住在伊豆的叔父所经营的潜水用具店“Grand Blue”。传入耳中的波涛声、炽烈照射的太阳、开始一起生活的可爱表姐妹……青春的大学生活！这样的伊织所面临的却是——除了野球拳以外的猜拳一概不知的强壮男人们！！刚一入学就被大学潜水社团“Peek a Boo”所盯上了的伊织，在会长时·田信治和三年级学生·寿龙次郎的怂恿下，不知不觉已经身为社团的一员加入了他们的愚蠢喧嚣中。在大学中认识的虽然长得帅但性格却很遗憾的宅男——今村耕平也加入其中，他们的青春向着越来越奇怪的方向转进。明明在寄住的地方有着可爱的表姐妹——古手川姐妹，但自己却被妹妹千纱当成垃圾看待，而姐姐奈奈华又是重度妹控，根本无法成为对象。在可爱的全裸笨蛋们的包围之下，伊织的大学生活究竟会变得如何……。