Episode 10: "The enemy is in Honnou-ji..." and what follows, especially when Nobunaga has Mitsuhide read what's on her sword.
Episode 4. When Nobunaga bests Shingen in combat, Shingen offers her the Takeda Clan' portion of the Crimson Armor, and asks that she take her head, unable to bare the shame of her defeat at the hands of someone other than her rival Uesugi Kenshin. Nobunaga is happy to oblige, to help Shingen retain her honor, but then Kenshin steps between them, offering her own head and portion of the Crimson Armor in exchange for Shingen's life. With a bond of friendship as strong as that, is it little wonder Hideyoshi saw them as such at the start of the episode?