Problems with the Master themselves could indeed cause problems with the Heroic Spirit they summoned.
Just like in the Fifth Holy Grail War, when Rin Tohsaka summoned the amnesiac Red A, Great Hero Emiya.
Clearly, the Lancelot summoned by Kariya Matou would be a lunatic. Aside from Lancelot's flaws being caused by insufficient mana, Kariya himself must have been a factor as well.
Hearing the kneeling Lancelot ask whether she was his Master, Sakura turned to look at Yoru Machi beside her.
Although Lancelot had been summoned by Sakura, and the Command Spells had appeared on the back of her hand, according to the rules of the Holy Grail War, she was unquestionably Lancelot's Master.
But Sakura herself had little interest in the Holy Grail. She had summoned a Heroic Spirit only to complete Yoru Machi's test, so when faced with her Servant's question, she instinctively looked at Yoru Machi beside her.
Yet Sakura's casual action immediately made Lancelot beneath his armor frown slightly.
As everyone knew, Lancelot was the strongest knight among the Knights of the Round and bore such esteemed titles as the "Knight of the Lake."
He had answered the Holy Grail's call because he wished to make amends for the mistakes he had once committed and serve a lord as a knight in pursuit of victory.
Yet despite having only just descended, Lancelot had already realized that his current lord seemed to be under someone else's control.
Since that was the case, as a knight, he naturally could not stand by and do nothing when he saw his lord being constrained against her will!
"Master, I will explain my identity in detail later. But before that, please allow me to remove the threat by your side."
Lancelot, who had been kneeling on one knee, suddenly rose.