Sae and Koki have been friends since childhood. One fateful day at the end of middle school, she has a revelation: Koki has grown up! Now they're in high school, and she has another revelation: she has feelings for Koki! But Sae isn't the only girl who does... The question is, who does Koki have feelings for?!

After waking from a long cryogenic sleep, high school student Akira Himegami finds himself in a world he no longer recognizes. The city lies in ruins from war, society is now governed by an organization called OWEL, and traditional marriage has been replaced by a new system known as "Elsie." As Akira struggles to comprehend this drastically changed future, a familiar figure appears before him—Yuugure, who bears a strong resemblance to his girlfriend Towasa. To his shock, Yuugure smiles gently and proposes: "Akira... please marry me." Confused by her sudden proposal, Akira agrees to travel with Yuugure, holding onto hope that somewhere in this world, the real Towasa is still alive. Along their journey, they encounter the evolving forms of love in this new era and reflect on what their bond truly means.

Like any proper noble lady, one must have certain acquired tastes. For Melphiera Marchalrayd, she just happens to crave a rather exotic protein—monsters! But do not judge! Despite its bad reputation, monster meat can be used in exquisite cuisine and Melphiera is determined to change the kingdom's opinion of it! Unfortunately, since debuting in society, Melphiera has been struggling to find her perfect match...until she meets the fearless "Blood-Mad Duke" of Galbraith!

The protagonists of the series are the three Kisugi sisters—Hitomi, Rui and Ai—who run a café called Cat's Eye. The sisters lead a double life as a trio of highly skilled art thieves, leaving cards with the name "Cat's Eye" at the scene of their crimes. They steal works of art that belonged to their long-missing father, Heinz who was a famous art collector during the Nazi regime, in the hopes of him contacting them. Toshio, the police officer investigating this case is the fiancé of Hitomi. He also swears to capture and bring down the Cat's Eye Gang.