The Sailor Scouts' return to peaceful bliss after the battle with Queen Beryl is short-lived when a strange object crashes into the Earth. Inside are two aliens, Ann and Alan, and they have one thing on their minds: survival. They assume the identities of Ann and Alan Granger, Earth brother and sister (though they are not truly brother and sister), and enroll in Serena's school as transfers from France (though they don't know a word of French). To survive, they must gather energy. To collect the energy, they enlist the help of the Cardians, mystical monsters that are represented by cards. They can be summoned by the music of an eerie flute Alan always carries with him. They are then sent off to gather energy. The energy they collect isn't just for themselves. They must also feed the Doom Tree, a giant tree they have brought with them. Their lives depend on its survival. But, just like with the Negaverse, Ann and Alan face the threat of the Sailor Scouts, and they soon encounter a new problem within themselves, something they don't know how to handle. In their short lives, the two have never encountered or felt love, and when they feel it for the first time, they can't understand it too well. Alan develops a crush on Serena while Ann falls for Darien. Eventually, this problem escalates to the point that each wants to destroy the other's crush. Just when things couldn't get worse, the Doom Tree goes wild. Fortunately, it all ends happily. Ann and Alan discover love and, realizing their error, leave to start a new life.