Kasou Ryouiki no Elysion

Kasou Ryouiki no Elysion summary:

An incredibly athletic older brother, Tenryu Taiga. A programming genius girl, Tenryu Fuyuki. The two siblings separated for eight 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 cyber world, the 《Aries》structure. Taiga after becoming a warrior in the game relying on his inborn senses, is puzzled by the unfamiliar sensation.
One day Saionji Rui, Fuyuki’s best friend appears and is attacked by a mysterious bug― “I’ll be waiting, my prince.”. Hybrid fantasy battle of cheating siblings begins here!