Karen has a lot of issues, however she is not the most troubled of the group nor is she the one who suffers the most. Yet, she does have a relatively sad story. Her father is the mayor of the island and a controlling dick. He tries to force her to marry someone against her will, and her mother abandoned her and her father 5 years prior to go live on the mainland. Needless to say, Karen has attachment issues and is seen throughout the whole series as being in her rebellious phase.

Sara has a similar backstory to Karen's, but it goes double for Sara in that she is all alone on the island without any parents. At least Karen has her father. Both of Sara’s parents were tragically killed in a fire years ago. Let’s not forget that Sara's uncle facilitates a facade of Sara as a miracle child to hide the fact that he was getting rid of all of the children with Soot Blight Syndrome. Sara seems to be spouting nonsense a lot with her frequent topics such as time travel and mysteries. She might know more than she is letting on, but she never comes out and says it. Either way, she has been all alone for five years and accepts her existence as cursed. Pretty dark, eh?

Rinne is the daughter of Kuon and the one who gives Setsuna a job so he can stay on the island and look for Rinne. Rinne claims that she suffers from the Soot Blight Syndrome that plagues the island. Rumor has it that sun exposure will kill you. So, she spends her days locked away in her mansion until Setsuna tricks her into going outside. Her mother is cold and distant and is locked up in her room constantly leaving Rinne all alone in the house. The worst part? She doesn’t even get the romantic ending but loses out to a Deus ex Machina setup.

Setsuna is where things start to get heavy. Note, this is full spoiler. So Setsuna is from a previous timeline where he and Kuon aka Rinne were trying to figure out a way away from the timeline they were trapped in. It never ever went well for them and the island is, in the past, suffering from a shortage of food and is ruled by a corrupt religion. It gets worse though because while they do succeed and Setsuna does make it to another timeline, he has no memories. He has to then build a relationship with the current timeline’s Rinne all in order to find out that she is not the Rinne that he has been seeking. She is his daughter!

Kuon obviously has the worst backstory in that it is so sad. Right before she and Setsuna manage to finish the time machine, the two make love resulting in Kuon’s pregnancy. However, she does not tell Setsuna, fails to realize the limitations of the time machine, and away Setsuna goes. She is forced to give up Rinne to the family she works for to avoid an abortion and somehow manages to live, secluded for years while Rinne grows up right before her very eyes. She then willingly gives up her chance at happiness in order to secure Rinne’s. It’s only by a stroke of fate that Setsuna remembers what happens and puts the pieces together to realize that Kuon is the Rinne of his timeline. She does get her happy end though thankfully.