Sonomi Daidouji is Tomoyo's mother and Sakura's first cousin once removed—she's the first cousin of Sakura's late mother, Nadeshiko. She runs a major toy corporation and is loaded, which comes up pretty often since she can basically buy whatever Tomoyo wants for her various projects.
The thing about Sonomi is that she was genuinely close to Nadeshiko, and she never really got over losing her. She blames Fujitaka, Sakura's dad, for Nadeshiko's early death, and she wasn't thrilled about their marriage to begin with. It seems like Nadeshiko got somewhat distanced from her family after marrying him, which only made things worse in Sonomi's eyes.
One quirk that shows how much Nadeshiko meant to her: she insists on keeping Tomoyo's hair long because it reminds her of her cousin. It's a small thing, but it says a lot about where her head's at.
Content compiled by AnimeList.moe from publicly available sources.
