In Vitro Shoujo -Nokosareshi Rakuen no Himegimi-

The protagonist, Hinata, arrives on Kindred Island, known as the last paradise for mankind. His objective is to guard the island's princess, Chiara Tiptree. However, Hinata is actually a spy sent in for a plan to kidnap Princess Chiara, planned to coincide with the island's spirit festival, which is scheduled to take place in a few weeks.

Chiara welcomes Hinata, but Flavia, who is also a guard, is suspicious of him. Hinata and Chiara are old friends. Moreover, they become aware of each other. When the two meet again as adults, they grow closer, transcending the boundaries between guardian and guarded... What choice will Hinata make in the end?

[Translated from the official site]