FROM STRANGERS TO FAMILYWhen his father remarries, Yuuta Asamura winds up sharing a roof with a brand-new stepsister, who is also the hottest girl in his grade! But Yuuta and his new sister, Saki Ayase, have no delusions—they both carry trauma from their parents’ difficult divorces, and they agree to keep a respectful distance. As it turns out, however, the two have a lot in common, and slowly, cautiously, they grow closer. But is the emotion blooming between them simple admiration, famili...

IMAGINE SPACETIME X HYPER RELATIVITY Edition.The faster one moves in space, the slower one moves in time, and the faster one moves in time, the slower one moves in space. This is the basic theme of this book. It is a relation between space and time where time is nothing but a dimension like space. A tug of war of "c" between space and time is what makes the entity of spacetime exist. Where "c" is the speed of light. Thus, the speed of light is the speed of existenc...

When high schooler Yuuta Asamura learns his father plans to remarry, he’s not too bothered by the idea…until he finds out his future stepmom has a daughter! Her name is Saki, and to Yuuta’s surprise, she’s a beauty who’s made a reputation for herself as an unapproachable “bad girl.” But as he gets to know her, he realizes she’s not the person everyone says she is. Could he be the one she finally opens her heart to?

ROMANCE OVERSEAS? After spending their first New Year’s together, Yuuta and Saki grow even closer. February brings Valentine’s Day, a school trip to Singapore, and, in turn, new encounters and realizations. Yet despite these special events, the pair must maintain a certain distance in order to keep their secret, and so they feel lonely even when together. What will happen when the stepsiblings, who have always kept themselves in check, begin to explore a new, more selfish kind of happiness...

ALL WORK AND NO PLAY ... It’s Yuuta and Saki’s first summer vacation as stepsiblings, and they’ll be working at the same bookstore! As Saki’s coworker, Yuuta begins to see a side of her he hadn’t noticed before. But after observing her new coworker for a while, Shiori makes a dark observation—if Saki doesn’t ease up and stop pushing herself so hard, sooner or later she’s going to fall apart. In order to help her, Yuuta will have to make a decision. Should he interfere in his stepsister’s l...

JUST SIBLINGS, OR SOMETHING MORE?Yuuta and Saki begin a secret double life and a relationship they can’t name—they’re still siblings, but they’re also teens who might just be in love. It’s time for new experiences, like going on their first date, getting into fashion, attending a friend’s birthday party, and celebrating Halloween. They’ve lived their lives without expecting anything from others, but as they spend more and more time together, those feelings begin to change. And gradually, t...

Astrophysics and Cosmology for Non-mathematicians is a combination of Astrophysics for Non-mathematicians and Cosmology for a Newbie.

TAKING SOME TIME APARTWhen Saki called Yuuta “Big Brother,” it looked to everyone else like their relationship had taken a big step forward. But in reality, it was more like a line drawn in the sand. As their hidden feelings make being together increasingly awkward, the two of them explore new relationships and weigh their priorities. Are some things worth holding on to despite the consequences, or is it time to let go and move on?

A month has passed since Yuuta and Saki have become siblings. They agreed to keep a respectful distance from each other, but when Yuuta’s attractive coworker asks him out on a date, Saki finds a strange new emotion welling up in her heart…

Yuuta and Saki have decided to hide their feelings for each other, choosing instead to live as brother and sister. But suppressing their emotions isn’t easy, and even as Yuuta tries to turn his attention to other women, it only makes him realize how special Saki is to him. And Saki isn’t faring much better…

It’s Yuuta and Saki’s first summer break as stepsiblings. Now that Saki has gotten a job at the bookstore where Yuuta works, they’ve ended up spending more time together, but she seems really stressed. When she even turns down an invitation to go to the pool with everyone, Yuuta decides to figure out what’s going on and help her relax. In the process, he finds himself thinking of her in ways that a brother shouldn’t…

Saki and Yuuta have finally found a small group of people who accept their relationship, but big changes are coming for them as they enter their final year of high school. The pair must navigate being in the same class, preparing for college entrance exams, and planning for the future as they approach their new family's first anniversary. They've grown so much closer over the past year, but it may be time to reevaluate that distance.