Unbelievably for Ryuto, his relationship with Runa has reached the one-month mark without issue. Runa, on the other hand, is secretly worried about the approaching "two-month barrier" all of her previous romantic relationships hit.

For their one-month anniversary, the couple takes a trip to Enoshima for a wonderful date on the beach. However, when dangerous weather rolls in unexpectedly, Ryuto and Runa find themselves stuck on the island, forced to spend the night together...

And as one storm passes, another grows—Runa's twin sister, Maria, has plans for Ryuto. They say all's fair in love and war, and she's not about to play nice!

While Runa and Ryuto's relationship will be put to the test, this unforgettable summer vacation is only just beginning!