Tarnished Are the Stars by Rosiee Thor
A secret beats inside Anna Thatcher's chest: an illegal clockwork heart. Anna works cog by cog -- donning the moniker Technician -- to supply black market medical technology to the sick and injured, against the Commissioner's tyrannical laws. Nathaniel Fremont, the Commissioner's son, has never had to fear the law. Determined to earn his father's respect, Nathaniel sets out to capture the Technician. But the more he learns about the outlaw, the more he questions whether his father's elusive affection is worth chasing at all. Their game of cat and mouse takes an abrupt turn when Eliza, a skilled assassin and spy, arrives. Her mission is to learn the Commissioner's secrets at any cost -- even if it means betraying her own heart. When these uneasy allies discover the most dangerous secret of all, they must work together despite their differences and put an end to a deadly epidemic -- before the Commissioner ends them first.
Nathaniel is one of the main characters with several chapters in his view where he starts by saying he’s never really been drawn to anyone. It’s only much later in the story, toward the end that he’s introduced to the terms asexual and aromantic. They’re the first time he’s heard the words.