Released on November 20th (Saturday) by Fantasia Bunko.
Itohara Touma, now a second-year high school student, has close friends and is leading a fulfilling high school life.
The only thing is, he has no romantic prospects.
He has a younger sister, and there was a girl who often came over to play since middle school, but—.
| Published | Title | # |
|---|---|---|
| 2021/12/30 02:00 | Episode 38 | 39 |
| 2021/12/18 20:34 | Episode 37 | 38 |
| 2021/12/18 18:44 | Episode 36 | 37 |
| 2021/12/18 07:02 | Episode 35 | 36 |
| 2021/12/17 17:14 | Episode 34 | 35 |
| 2021/12/16 22:54 | Episode 33 | 34 |
| 2021/12/16 14:27 | Episode 32 | 33 |
| 2021/12/16 11:53 | Episode 31 | 32 |
| 2021/12/16 01:09 | Episode 30 | 31 |
| 2021/12/15 21:14 | Episode 29 | 30 |
The story begins by introducing Itouhara Touma, a second-year high school student, and his younger sister, Saki, who is a year his junior. Despite their frequent squabbles, they maintain a close relationship, managing household duties while their parents are busy. One day, Saki asks to invite her friend, Mamiya Rin, over. Touma, unaware of the future implications, readily agrees. Rin, a strikingly beautiful and polite girl, makes a strong impression on Touma. As Rin and Saki become inseparable, Rin frequently visits, often left waiting by the habitually late Saki. During these times, Touma and Rin develop a unique, somewhat awkward closeness, engaging in conversations that Saki remains oblivious to.
As spring break ends, Saki informs Touma that Rin will be attending his high school, while Saki herself will go to a music-focused school. Touma, a member of the "go-home club" (no club activities), initially dismisses the idea of actively engaging with Rin, though he's willing to help if she's in trouble. His friends, the popular and athletic Haruki and Yukito, tease him about his lack of a girlfriend and club activities. Touma, despite being physically capable, is generally lazy and has no particular romantic interests.
On the first day of the new semester, Rin surprises Touma by visiting his classroom. Dressed in her new uniform, she appears more mature and beautiful. She formally reintroduces herself, almost calling him "Onii-san" out of habit, then blushes. Touma's classmates are abuzz with curiosity, and his friends immediately assume a romantic connection. Touma vehemently denies this, explaining Rin is merely his sister's friend. Internally, he grapples with his growing awareness of Rin's charm, determined to maintain his role as a supportive older brother to protect Saki's feelings and their family dynamic.
Later, at home, Touma recounts Rin's visit to Saki, who is delighted by the interaction. Unaware of the subtle shifts in their relationship, Saki enthusiastically suggests Touma and Rin exchange contact information, revealing that Rin often asks about him. Touma reluctantly complies. Rin's first message teases him about his past avoidance of exchanging numbers, revealing her sharp memory and a more assertive, playful personality when Saki isn't present. A flashback reveals Touma had tutored Rin in middle school, helping her prepare for high school entrance exams, a period where their bond deepened. Rin expresses deep gratitude, stating she wants to make him happy.
The next day, Touma, sleep-deprived from their late-night messaging, is greeted by Mikami Yuka, the energetic class representative. Yuka, a popular, stylish, and academically brilliant student, playfully questions Touma about Rin, again assuming a romantic link. Touma denies it, and they discuss Yuka's high standards for a partner and her dislike of rumors. Touma praises Yuka's unique ability to bend school rules with style while maintaining perfect academic and leadership records. Yuka, finding Touma interesting, suggests they exchange contact info, which he accepts, forming a new, casual friendship.
After school, Rin invites Touma to walk home together. She expresses disinterest in joining clubs, particularly as a manager, citing a dislike for handling dirty clothes and potential "complicated male-female relationships." Touma explains his own reasons for not joining clubs, stemming from a middle school kendo injury. Rin playfully calls him "lazy" but then subtly maneuvers him into agreeing to tutor her again after school, framing it as their "study club." She playfully whispers that she'll be his "exclusive manager," causing Touma to blush and realize Rin is "more dangerous than he imagined."
Back home, Touma tells Saki about the "study club." Saki, surprised by the rapid development but still oblivious to the underlying romantic tension, approves, seeing it as Touma being helpful to her friend. Touma, meanwhile, struggles to suppress his burgeoning feelings for Rin, reaffirming his desire to remain *only* a supportive older brother to avoid hurting Saki. The dynamic between Touma and Rin has clearly shifted from distant politeness to a more intimate, teasing, and emotionally charged connection, challenging Touma's carefully constructed boundaries.
 | Amazon.jp https://www.amazon.co.jp › My Sister... At first, he was just a friend of his sister's. But things didn't stay that way. Is there a "next step" to friendship between a man and a woman? Toma Itohara isn't interested in romance. He's comfortable in relationships where there are clear boundaries... |
 | Kakuyomu https://kakuyomu.jp › works It will be released by Fantasia Bunko on Saturday, November 20th. Toma Itohara is now in his second year of high school, has good friends, and is enjoying a fulfilling high school life. If there's one thing I can say, it's that he... |
 | Become a Novelist https://ncode.syosetu.com › ... My sister's best friend? My female friend? Then what's next? Author: Epanterias... Released on November 20th (Saturday) by Fantasia Bunko. Toma Itohara, now a second-year high school student, is... |
 | Fantasia Bunko https://fantasiabunko.jp › product 20 Nov 2021 — At first, he was just my sister's friend. But things couldn't stay that way. Is there a "next step" to friendship between men and women? Itohara Toma has no interest in romance. |
 | Book Walker https://bookwalker.jp › series Mamiya Rin is my younger sister's friend and often comes over to our house to play. At first, our relationship was just that—I helped her with her studies, we went to the same school, we started walking home together, and gradually our relationship became more like "my younger sister's..." |
 | Bookmeter https://bookmeter.com › books Here are reviews and comments for Epanterias' "My Sister's Best Friend? My Girlfriend? Then, What's Next?". A free sample of the e-book version is available. Reviews and comments containing spoilers are... |
 | Comic Seymour https://www.cmoa.jp › title Mamiya Rin is my younger sister's friend and often comes over to our house to play. At first, our relationship was just that—I helped her with her studies, we went to the same school, we started walking home together, and gradually our relationship became more like "my younger sister's..." |
 | Random notes https://yamata14.livedoor.blog › a... 16 Mar 2022 — At first, he was just my sister's friend. But things couldn't stay that way any longer. Is there anything "next" to friendship between a man and a woman? Itohara Toma has no interest in romance. |
 | Mekrimequru https://mequrimequru.jp › series My sister's best friend? My friend? So what's next? At first, she was my sister's friend. But things didn't stay that way. Epanterias (author) / Shiina Kuro (illustration). |
 | Rakuten Books https://books.rakuten.co.jp › ... My Sister's Best Friend? My Girlfriend? Then What's Next? (1) (Fantasia Bunko). Epanterias. Released November 20, 2021 / KADOKAWA. 715 yen (tax included). In stock. A New Graduate Who Doesn't Like to Pay Attention... |