Tamayura: Bon Appétit

Norie Okazaki and Masanori sticking their forks into pastries

Created by and named after Masanori Okazaki’s energetic little sister, “Norie Sweets” are the perfect treat to eat while studying for exams, taking photographs, or relaxing on a midsummer’s day.
From the anime series Tamayura

Bubuki Buranki: Rivals

Close-up of Asuma Kazuki and Kaoruko angrily butting their heads together

Buranki are giant, sentient, robotic beings, and both Azuma Kazuki and his younger twin sister, Kaoruko, have the power to awaken and use the one known as Oubo, though they disagree over who has the right to possess its control-unit “heart.”
From the anime series Bubuki Buranki

Boku no Marie: Amazing

Marie Karigari smiles and holds her fists up triumphantly while Hiroshi Karigari watches agape

Hiroshi Karigari and his little sister, Marie, live together as normal siblings, even though she’s an android he built to look exactly like the girl he loves.
From the anime series Boku no Marie (My Dear Marie)

Onii-chan Dakedo Ai Sae Areba Kankeinai yo ne!: Let’s Do It

Akito Himenokoji sighs as Akiko Himenokoji gives him a thumps up while holding a pillow that says Yes on it

After six years of living apart, Akito Himenokoji reunites with his little sister, Akiko, only to learn that she’s developed a complex towards him.
From the anime series Onii-chan Dakedo Ai Sae Areba Kankeinai yo ne! (OniAi)

Flying Witch: Peace and Quiet

Kei Kuramoto and Chinatsu Kuramoto looking at a vast forest

The everyday life of Kei Kuramoto and his little sister, Chinatsu, becomes much more fun and interesting when their second cousin comes to live with them.
From the anime series Flying Witch

Arslan Senki: Battle Ready

Merlane stands with a spear while Alfreed runs in to the room

Merlane and his younger sister, Alfreed, are born of the Zot Clan, a fierce tribe of warriors, and its chieftain was their father.
From the anime series Arslan Senki (The Heroic Legend of Arslan)

High School DxD: Crimson Rulers

Sirzechs Lucifer and Rias Gremory facing each other. He's wearing ceremonial armor, and she's in a formal party dress.

Sirzechs Lucifer, by his own words, is the devil king first and an older brother second, but it’s a close second. Meanwhile, Rias Gremory is the Princess of Ruin in the underworld and a top-ranking student at her high school, as well as the president of the Occult Research Club.
From the anime series High School DxD