Hacka Doll the Animation

The anime personifies the app's customization engine as three "Hacka Dolls" — the personal entertainment AI and main navigator Hacka Doll #1 (played by Miyu Takagi), the anime expect Hacka Doll #2 (Kaya Okuno), and the knowledgeable otaku Hacka Doll #3 (Nanami Yamashita). The Hacka Doll's three voice actresses also sing the anime's theme song "First Heart Beat," while Reimi Yukarino voices the user.

(Source: ANN)