Sanada family (Masayuki and Nobuyuki)
Family who he cherished the most, ever since he was sent out as hostage from homeland, he had a very hard time meeting up with them.
He helped his father come out various strategies and aided the Defenses of Ueda Castle twice. He also supported Nobuyuki by his side and cheering him up.
Anything for the sake of the Sanada family...!
The Osaka Ronins
Naturally Yukimura is the most popular among them, but he never discriminates against anyone and fights together till the end. His comrades weren’t really close together at first but they all got along at the end after his first accomplishment.
“Woah, even my friends are here too! I'm impressed you managed to summon them, Master! Maybe I shouldn’t be too excited about this...”
Goto Matabei Mototsugu: The man who died first back in the Siege of Osaka, Always have a fight whenever they meet together. Yukimura almost couldn’t look him up because he failed to save him, almost wanting to end his life.
“Oh hey is Matabei...I am glad you’re here doing okay. Well I hope we can get along as Heroic Spirit!”
Mouri Katsunaga: A comrade who respected him the most as well as fought with him till the end. He stopped Yukimura from committing seppuku after the death of Matabei during the Siege of Osaka.
“Katsunaga? You’re here serving my Master too? I am looking forward to working as a teammate!”
Chosukabe Morichika: Yukimura attempts to take care of him and always encourages him really hard just to make sure Morichika is able to accomplish something new.
“Ah Morichika, are you doing well buddy? If you aren’t in a good mood today, I can just hang out with you inside the kotatsu.”
Akashi Takenori: He’s a strange Christian man, the strangest so far I’ve ever encountered in my life.
Toyotomi Hideyoshi
Hideyoshi really likes him, even go so far to recruit him as his guard, promote his court rank to Sanada Saemon-no-suke (真田左卫門佐). There's an anecdote where Hideyoshi attempted to claim him to be one of his relative. So it is natural for Yukimura to pledge him as his Lord.
Ishida Mitsunari
A purehearted general from the Toyotomi clan who guided Yukimura in Osaka Castle until Sekigahara War. He used to helped Mitsunari whenever he was in trouble. However, they probably never able to face to face whenever they have a chance to meet again....
Chacha
The Fallen (Wicked) Princess who has deep affection towards him but he tries not to be too involved with her after being summoned as Servant. He rather wishes to have someone else to take care of her.
“Princess Chacha is here?! And she’s having fun? …That’s good to hear, Master, please continue taking care of her for me, okay?"
Oda Nobunaga
He might had met Nobunaga once, right before the Honno ji incident. He’d be surprised to see how Nobunaga looked as a Servant. It might be different if he encountered Maou Nobu however…
“6th Demon King Oda Nobunaga...wait, she’s a female? Ah, no! There’s nothing wrong about that! Wait, you even have a swimsuit too? That’s really impressive for a Demon King...”
“Maou Nobunaga, so this is what her true colour looks like...”
Uesugi Clan
Uesugi Kagetsugu: Kagetora's nephew, The Uesugi Daimyou who took Yukimura as hostage but treated him as a guest due to his great impression while asking for protection from the Tokugawa/Hojo Clan. He genuinely had a great time in Echigo as a hostage.
Nagao Kagetora: Uesugi Kenshin who is called her(him)self as "God of War". Since he has a connection with Uesugi Clan as a hostage (guest), where he met Uesugi Kagekatsu and Naoe Kanetsugu
“God of War Nagao Kagetora is here too? I want her to teach me everything as general onegai- Huh, first I have to praise Bishamonten? You’re joking right?”
Naoe Kanetsugu: Uesugi Kagekatsu's Chief Retainer. They don't know they were sharing similar situation in their life so they suppose can relate the pain each other? All they did are just smiling awkwardly I suppose...
Date Masamune
Yukimura first met Masamune after the Battle of Odawara and made a secret pact later on. Masamune also respected The Sanada family really well. The Date Clan gave Yukimura's Family protection after the Siege of Osaka and had one of his daughters married to Katakura Kagetsuna(Kojuro)'s son.
Takeda Clan
Yukimura didn't have any relation to Takeda clan solely because he was still young before the fall of Takeda clan and never involved with Takeda clan before. So he is barely able to relate nor know anything personally with them. So you shouldn't be surprised by his plain response.