This is based on opinion. Please don't list it on a work's trope example list.
Tear Jerker / Hibiki no Mahou
Nearly every chapter has a tear-jerking moment.
The death of Shirotsuki's human body in the first chapter, leaving Hibiki alone in the world.
Ahito's backstory. He was in love with a young girl named Mizuki whose magic, like all magic, came with a price. The more she slept, the deeper she slept until one day she'd never awake. Ahito agreed to undergo torturous experiments to gain magic of his own, which would heal her at the cost of his life force. One day, the cost of his magic nearly killed him, forcing a hospitalization. When he woke up, Mizuki was dead, and the magicians watching over them were more interested in her powers than her. This incident caused him to renounce all magic.
The old man's story about his son, which he tells to a friendly demon. His son was gentle and loved flowers, and to have such a son vexed the old man, but he dearly loved him. One day, his son went off to war and never returned. He asks the demon that, should she find him, to tell him the war is over and he can come home.
Yukko created many homonculi to try and bring her dead daughter back to life, but they all ended up as blobs of jelly which fell apart after one day. In the end, her daughter's magic tears are used in a potion to save Shi-chan.
Shirotsuki's magic made him lose his memories, including the person he loved, Yui. He forgets her multiple times, and she's shown breaking down from the strain.
The monster that used to be a girl. Hibiki throws the girl's hat on the monster, and the monster dies after finally feeling human.
Shiiraasan gets her hands on a packet of magic crayons. But they can't create living things, leaving her with only a drawing when she tries to draw the person she wants with her most.
One three-part story arc revolves around a childhood friend of Asuma's whose ambition drove him to an early grave, and another is about Ahito's Dark and Troubled Past seemingly coming back to haunt him... and Hibiki getting caught up in an accident that almost kills her.