It could be Jiraiya. They have a long - standing relationship. Jiraiya has always been around Tsunade, and they have a deep connection. His carefree yet passionate nature might be what Tsunade needs in a partner to start a family with.
Jiraiya is also sometimes considered a close friend in fanfics. Given their shared history as part of the Sannin, there are fanfics that explore their complex relationship. They may have had adventures together in their youth and still hold a special place for each other in their hearts.
Tsunade, of course, is the central figure in her own love story. Then there was Dan, the man she deeply loved. He was an important part of her life before his untimely death. And Jiraiya, who was not only her friend but also someone who had a special place in her heart, with a relationship that was a blend of friendship and something more, though not fully explored.
Perhaps a new character could be the main antagonist. This new character could be a powerful ninja from another village who has some sort of connection to Konoha. They might be influencing Tsunade's decisions in a negative way, for example, by making deals that Naruto sees as harmful to Konoha. Naruto snaps at Tsunade because he doesn't understand why she is going along with this new character's demands. This new character then becomes the main source of conflict as Naruto tries to expose their true intentions and fix the rift between him and Tsunade.
Well, Naruto himself could be involved. He might be concerned about Tsunade's pregnancy and offer his support in some way, like running errands for her or helping to keep the village in order while she's dealing with her pregnancy.
Zichu's father was King Xiaowen of Qin. The father of King Zhuang Xiang of Qin, Ying Zichu, was King Xiaowen of Qin. King Xiaowen of Qin was the father of King Zhuang Xiang of Qin, and also the grandfather of Ying Zheng, the First Emperor of Qin.
Tsunade's character might develop by becoming more maternal towards Naruto. Saving him could make her see him as more than just a village ninja. She could start to care for him in a more personal way, like a mother figure.