Natsu-Mon! 20th Century Summer Vacation puts gamers in the shoes of the guy, the ringmaster's son, immersing them in the quaint charm of a small village in the summer of '99. The action takes place in a 3D environment with an open setting, allowing players to explore a variety of places – from serene mountains to the alluring ocean, from a sacred temple to a bustling city center. The main appeal of the title is that it promises a soulful and leisurely relaxation. Users can engage in various activities that convey the essence of a carefree summer: fishing, collecting insects, keeping a diary, helping the circus, participating in a summer festival.

Natsu-Mon! 20th Century Summer Vacation doesn't stop there, introducing a dynamic weather system that effectively changes the atmosphere of the village. Combined with the cycle of day and night affecting the events that unfold and the activities available, the title strives to create an interesting and nuanced gameplay experience. Within one month, gamers must make choices that will ultimately determine the outcome of their virtual vacation. Depending on the decisions made during gameplay, players are offered several endings. The video game absorbed the spirit of nostalgia and freedom of childhood, giving users the opportunity to relive the joys of a bygone era and create their own unique story in a charming setting.