ELYSION virtual region (Kasou Ryouiki no Elysion, 仮想領域のエリュシオン) is a light novel series written by Kazuma Jouchi (一麻 上智) and illustrated by nauribon (なうりぼん).
Published by the MF Bunko, the series is complete at three volumes.

Story Synopsis

An incredibly athletic older brother, Tenryo Taiga. A programming genius girl, Tenryo Fuyuki. Siblings separated for 8 years ended up living under one roof again, after facing the problem – a lack of funds for living expenses. Fuyuki proposes a way to earn money, a core system deeply involved in people's daily lives, a game that awards you money as a prize for defeating malicious bugs in the cyber world, the 《Aries》 structure. Taiga relying on his inborn senses becomes a warrior in the game, and is puzzled by the unfamiliar sensation of the game world. One day Saionji Rui, Fuyuki's best friend appears and is attacked by a mysterious bug― “I'll be waiting, my prince.”. The hybrid fantasy battle of cheating siblings begins here!

Volume 001_Synchro infinity (Full Text)

• Novel Illustrations
• Prologue - The Day They Returned to Being Siblings
• Chapter 1 - Moving In, School, and The Cyber World
• Chapter 2 - First Suppression
• Chapter 3 - Rampage, and a Chance Meeting
• Chapter 4 - A vow to Uphold
• Chapter 5 - Area of The Fastest and The Strongest
• Epilogue - A Road Far Away, Aiming for The Sky
• Afterword

Volume 002_Hydrangea garden (Full Text)

• Novel Illustrations
• Prologue - Banquet of The Influential Ones
• Chapter 1 - Reunion With The Past
• Chapter 2 - The Light and The Shadow
• Chapter 3 - Resolution to Confront The Past
• Chapter 4 - Karasuba Fuyuki and Karasuba Shio
• Chapter 5 - Bonds of Hydrangea
• Epilogue - The End, and The Beginning
• Afterword

Volume 003_Cerulean requiem (Full Text)

• Novel Illustrations
• Prologue - Chance Meeting
• Chapter 1 - Light of Everyday Life
• Chapter 2 - Quickening's Silence
• Chapter 3 - Countdown
• Chapter 4 - Banquet of The Dead
• Chapter 5 - Requiem Played In The Sky
• Epilogue - The Proof She Once Lived
• Afterword