Following the events after Lume, Lumi embarks on another journey to get back her Grandad after being captured. Join her quest to find her Grandad as she explores the unusual yet beautiful Lumino City and tries to find out more of her Grandad's mysterious life along the way.
The game starts right where Lume left off, with Grandad about to tell Lumi about what happened at the village. But before Grandad shares on what had happened, he asks for a cup of tea and says that he wants to show Lumi a book. As Lumi is in the process of making tea, she suddenly hears someone breaking in and taking Grandad away, who tells her to go to the city before his kidnapping. As she was about to exit, she spots a book entitled The Handy Manual, the book Grandad wanted to show her, which contains many diagrams, instructions, and hints on future puzzles.
As Lumi finds her way to the entrance of a city called Lumino City,
- The title is a pun of the word "luminosity", which is a measurement on the brightness of a light.