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Tear Jerker: Nanatsu No Taizai
In Chapter 8, Diane then told Elizabeth that she always wanted to be small, and can't even get close to someone she loves due to her height and always envy regular size girls.
In Chapter 11, Elizabeth end up blaming herself for all the trouble that has been happening to Meliodas and the doctor, but Meliodas then cheer her up by telling her that he will continued to try and stop the Holy Knights even if she were to die.
In the same chapter, it reveals in a flashback that Meliodas knew some unknown female named Liz who died unknowing which made even Meliodas shed tears, it was then reveal that woman is someone Meliodas consider the most important person in his life.
In Chapter 23, King keep on questioning why he can't see his dead sister Eliane which then he found out that the reason is because she is still mad at him for leaving his kingdom and his sister behind which made King sheer tears.
In Chapter 39, in the battle between Meliodas and Cain, Cain give on tossing fire ball at Meliodas and keep on asking him in tears why he betray everyone he loves in Danafor which the latter keep on letting Cain attacking him, possible still feeling guilty over the fate of Danafor for many years.
In the Side Story, everyone believed that Ban is the one who killed the guardians saint Elaine just to gain immortal, but then it was revealed that Ban became great friends with Elaine who the latter end up having feelings for him, Ban even go so far to promise her to bring her brother back to set her free, but end up going bad when a demon shows up and kills them both and Eliane end up giving the Fountain of Youth to Ban in order for him to live.
The reason Ban even wanted the immortality was to see if anything good will happen to him in his life, which in his childhood, he was having a rough life.
Made even worse when you consider the only reason that Elaine was even in the position she was was because King, for some currently unknown reason, had abandoned his post as guardian. This combined with the revelation mentioned above leaves King understandably broken.
After finding out who Armando (Gowther) really is, Pelio broken down in tears, thinking his friendship with him was a lie.
Seeing Diane defeat and treat badly by the town folks of Liones was heart breaking as she still continued to move just to save Elizabeth who is now her friend and kept on saying that she was always alone.
In a Side Story, we learn King's backstory, and it is as bad as Ban's. We learn King left his post to find Helbram who had been attacked. In the attack, a bunch of humans that attacked fairies for their wings. In the attack King lost his memory, and he found a young Diane. They spent years together, King eventually regained his memory. One day, King heard an attack and left Diane to check it out. He found out that Helbram survived and had been spending centuries murdering humans for the humans once attacking Fairies and brutally ripping off their wings. King was forced to end his incapacitate him. He then erased Diane's memory, as he felt he had sinned too much. And he and Helbram was taken to jail.
Even better, we learn about how King and Diane's relationship really started. She found him in the river and gave him a place to recuperate. In return, he was a constant companion to the loner and the source of the look she has now. They become so close that she sweetly asks King to always love her. She knows that King needs to go find Helbram so she tells him to leave. He promises to come back once he is done. However, everything goes wrong and he couldn't be there for his kingdom, his sister, his best friend or his love interest. Can you blame him for feeling a bit under the weather?
Diane: 'Harlequin'. That name sounds really nostalgic but...I can't remember who that is.
King: (with the most heartbreaking smile every) It was probably just a dream