Read manga: Saikin, Imouto No Yousu Ga Chotto Okashii N Da Ga.

manga
Summary:

High school girl, Kanzaki Mitsuki, just got a new older brother when her mother remarries a man with a son. Soon after, her new step dad gets transferred overseas and her mother follows him there, leaving Mitsuki alone with her new step brother, Yuuya. Feeling abandoned by her mother, she stays distant from Yuuya, never really getting along very well with him nor even keeping a conversation with him, until one day ....

Chapters (63)
Aug 25, 2019
Chapter 1
Aug 25, 2019
Chapter 2
Aug 25, 2019
Chapter 3
Aug 25, 2019
Chapter 4
Aug 25, 2019
Chapter 5
Aug 25, 2019
Chapter 6
Aug 25, 2019
Chapter 7 : Do You Still Remember Me, Onii-Chan...?
Aug 25, 2019
Chapter 8
Aug 25, 2019
Chapter 9 : Ha..the..time..when My Body..!
Aug 25, 2019
Chapter 10
Aug 25, 2019
Chapter 11
Aug 25, 2019
Chapter 12 : I Will Strike At Once Tonight!
Aug 25, 2019
Chapter 13
Mar 23, 2020
Chapter 14: Jealousy? Nope Nope Nope!
Mar 23, 2020
Chapter 15: It Doesn't Have Anything To Do With Me!
Mar 23, 2020
Chapter 16: It Feels Like... I'm Tied Up Or Something?
Mar 23, 2020
Chapter 17: Dinner? A Bath? Or Maybe...❤
Mar 23, 2020
Chapter 18: Date?! Is This Really A Date...?
Mar 23, 2020
Chapter 19: What If You Were To Lose Your Self-Control?
Mar 23, 2020
Chapter 20: What Is This? I Feel So Sensitive...!
Mar 23, 2020
Chapter 21: Did I Do Something To Make You Cry?
Mar 23, 2020
Chapter 22: You're Wrong! Yuki-Chan Is A Boy!
Mar 23, 2020
Chapter 23: I'm Supposed To Be This Guy's Girlfriend?
Mar 23, 2020
Chapter 24: Hey, What Should I Call You?
Mar 23, 2020
Chapter 25: She's Just Playing Around, And That Sort Of Thing.
Mar 23, 2020
Chapter 26: Together With Yuu-Kun, In Mitsuki-Chan's Body...
Mar 23, 2020
Chapter 27: Is It Relaxing, Being With Her?
Mar 23, 2020
Chapter 28: About This Morning...
Mar 23, 2020
Chapter 29: So, How's It Look From Your Side?
Mar 23, 2020
Chapter 30: I Want It Directly From Onii-Chan
Mar 23, 2020
Chapter 31: Can I... Sit With You?
Mar 23, 2020
Chapter 32: If I Were To Talk With Mom Now...
Mar 23, 2020
Chapter 33: Then... Hold Me Tight Right Here!
Mar 23, 2020
Chapter 34: Ahh, Geez! What Should I Do, Then?
Mar 23, 2020
Chapter 35: Even Though They Love Each Other So Much...
Mar 23, 2020
Chapter 36: An Amazing Feeling Of Liberation
Mar 23, 2020
Chapter 37: Want To See... More?
Mar 23, 2020
Chapter 38: If Only You Could Call Him By Name...
Mar 23, 2020
Chapter 39: He's So Small... And So Cute.
Mar 23, 2020
Chapter 40: Something's Wrong With Me.
Mar 23, 2020
Chapter 41: Thank You, Yuuya... Onii-Chan.
Mar 23, 2020
Chapter 42: So You Like Both Of Us?
Mar 23, 2020
Chapter 43: And Also... Because Of My Own Feelings
Mar 23, 2020
Chapter 44: Alright, Let's Work Together
Mar 23, 2020
Chapter 45: How Did I Forget?
Mar 23, 2020
Chapter 46: I Can't Just Sit Here And Do Nothing.
Mar 23, 2020
Chapter 47: For Some Reason, This Is Really Embarrassing...
Mar 23, 2020
Chapter 48: I Still Like You, Even Now.
Mar 26, 2020
Vol.11 Chapter 49: Thank You... Yuki-Chan
Mar 28, 2020
Vol.11 Chapter 50: This Has Happened Before, Hasn't It?
Mar 31, 2020
Vol.11 Chapter 51: Are You Okay With This, Mitsuki?
Apr 02, 2020
Vol.11 Chapter 52: This Is... A Kiss, Right?
Apr 09, 2020
Vol.11 Chapter 53: You Have To Go... Right?
Apr 10, 2020
Vol.11 Chapter 54: I'm Back, Onii-Chan.