Legacy of Chaos by Larissa Ione

Stryke, son of Shade and Runa, grew up a happy, well-adjusted incubus alongside his four brothers. A supergenius, he took an interest in science and technology at an early age, with a dream of joining NASA…until a moment of carelessness resulted in the death of his little brother. Unable to forgive himself and desperate to prevent a similar tragedy from happening to others, he started up his own anti-demon tech company and sequestered himself behind its walls. Now he’s a household name and one of the wealthiest people on the planet.
Cyan, a technomancer who works as a cybersecurity expert for DART, lost her best friend to a weapon designed by Stryke’s company. She’s hurt, angry, and wants revenge. So when an opportunity to work with Stryke on a project arises, she jumps at the chance to help DART and make Stryke’s life miserable.
At first, Cyan and Stryke butt heads about everything. But she soon finds that deep down, he’s desperately wounded and willing to sacrifice everything, including his family, to achieve his goals. Can she help him heal before he destroys himself—and everyone around him?