Tomoyo has become a heavily armed, extremely well funded, psychotic hitman for Sakura.
Batman is summoned as a Servant. The Goddamn Batman is summoned as a Servant Not only that, he is summoned as Berserker. Then, he makes it plausible that someone so straight-lacedas Batman can fit into Berserker Class.
Foe Yay: Signum/Yuuno, Signum/Tuxedo Kamen, and Signum/Fate. It's parodied in an omake in which Fate finding evidence of Signum's fight with Tuxedo Kamen is treated like an affair.
God-Mode Sue: Tomoyo is skilled with blasters and katana and has been trained by such diverse teachers as Slade Wilson, Tsukuyomi and Konoha ninjas who are also on her payroll as bodyguards; for Sakura, of course, not herself. She has the personal budget and connections to purchase black market anti-mage mutions. To top it all off, she can detect the Goddamn Batman's Stealth Hi/Bye!