Beautiful sisters Ai, Mai, Mii, their android maid Mea and slippery pet ferret Unagi make an amazing journey together through time and space without ever leaving their beloved mansion behind! Following the clues of the strange dandelion-like "Popotan," the girls are theoretically seeking the person who has the answers to their most personal questions, but they seem to have more than enough time to take side trips, meet new friends, visit hot springs and occasionally operate the X-mas shop they keep in the house along the way! Yet, the girls' ultimate destiny holds more than a few surprises of its own, and not every moment is filled with hilarity, as moving through time means having to leave friends behind as well.

The story is set in Aquafall, a fantasy world abound with water and greenery, and populated by dragons and fairies. Meteorites suddenly bring forth evil creatures that threaten all living things on the planet. The fairy Syrup assembles the Aquafall Defense Force, with three girls of the dragon clans as recruits. The story follows Syrup and the dragon girls Leviathan, Bahamut, and Jörmungandr as they work together to battle enemies and grow up.

The story takes place in a trading city Ert'Aria. Leicester Maycraft is an item engineer belonging to an adventurer guild "Oasis." One night, he is at a party with his friends to see a meteor stream on the rooftop of a chapel. One meteor grazes them and hits the steeple of the chapel. There he finds a secret room and a sleeping girl. The girl wakes up and says "You must be my father!" The encounter with the mysterious girl brings an unexpected adventure to Leicester.

For high school students like Shouichi Kamita, university entrance exams and the future are common concerns. It is also during this time in life that a mysterious emotion that vexes people of all ages may begin to weigh upon one's mind—love. At this point in his teenage years, Shouichi finds three girls he could see himself having a future with: the ever-cheerful Hikari Tsuneki, who teases Shouichi without mercy, but actually has a softer side; the competitive gamer, Tooru Miyamae, who has difficulty communicating with others; and Shouichi's childhood friend, Kyouko Touno, the sometimes immature shoujo manga enthusiast. Seiren follows Shouichi's relationships with these three girls across three separate arcs, as their feelings grow from mutual interest and blossom into something more beautiful. [Written by MAL Rewrite]