Takiboku's past, being The Last of His Kind of the Quaing clan not an alien in the manga, and having to live with the guilt for 60 years is pretty sad.
Bunchu deciding to kill himself, then seeing King Zhou once last time before being sealed.
In the manga, King Chuuou's final days. After becoming a Body Horror abomination, he is abandoned by Dakki and left in a confused, pitiful and nearly catatonic state. He is saved by Outenka before Kou Tenka manages to deal the final blow, only to be taken to his decaying capital where he finally sees the terrible suffering that his rule has brought onto the people. The body alterations Dakki has given him are starting to take its toll, and he begins looking more and more haggard and old. When a desperate mother tries to kill him, he accepts his fate with quiet resignation, but soon realizes that Dakki has made his body very difficult to kill. He returns to his palace only to be humiliated by his own guards who failed to recognize him and orders them to open the gates and divide the food found in the palace among the people. Then he returns, exhausted and saddened, to his dark and solitary throne room. By the time he is executed, he realizes that he has nobody to protect or to fight for anymore because everybody he loved is dead: his wife Kyouhi, his children, his vassals Bunchuu and Kou Hikou.
The real heartbreaking part is that after years and years of alternating between a clown and a meat puppet, toward the end he begins acting less and less like Dakki's pawn and more and more like his former self. He regains a part of his spirit, shows genuine remorse and pain for the suffering he has caused and dies with dignity. His final hours really emphasize just how much he lost and how much he has been victimized by Dakki.
The real So Dakki's fate. She was a sweet, gentle girl willing to sacrifice her personal happiness for the sake of her country and she was essentially killed by the fox sennyo and had her body stolen. The sennyo proceeded to use her identity to commit horrible acts and to torture the people, causing great anguish to everybody, making Dakki go down in history as a monster. Even worse, her own father and brother have no idea what truly happened to her and think that the fox sennyo really is their daughter and sister. Her own family believes that she committed those terrible acts, and are glad to get rid of her...
The entire battle between Taikobou and prince Inchao is heart-wrenching. Made worse through prince Inhon's death and the fact that it doesn't sway his older brother.