“Thank you for letting me know. Still, Tsubaki’s Servant seems to be in the process of becoming practically unassailable, so I’m sure it will see her through this safely.”
“It’s . . . becoming unassailable?”
“Yes, just a bit before you woke up, it sent us a wonderful guard dog.”
“What do you mean?” Sigma asked just as Assassin approached them.
Sigma tried to stop Yūkaku, who was ignoring him and making his way home, but he saw that Assassin had a grim look in her eyes, decided that something must have happened, and decided to stop to hear what she had to say.
“What’s wrong?”
“. . . It appears that your conversation was . . . overheard.”
“. . .?”
“When you said, ‘Tsubaki is being targeted,’ it began to move.”
She turned her gaze toward Tsubaki’s house as she spoke.
When Sigma followed her gaze . . . time froze for him.
His brain was unable to grasp the situation. For fractions of a second, his mind went blank.
The thing that did that to a magecraft-user like Sigma, with his long experience as a mercenary . . . was a single large dog.

Fate/Strange Fake: Volume 6, Interlude ("Mercenary, Assassin, Pale Rider")