This is based on opinion. Please don't list it on a work's trope example list.
Tear Jerker / Tokyo Magnitude 8.0
In episode five we see that one of Mirai's classmates has lost her mother in the earthquake. She only appeared for a brief scene and Mirai herself said they weren't even friends however it's still tragic, especially since it was so close to home for Mirai and it serve as a Mood Whiplash after one of the few times we see her genuinely happy.
In the same episode we learn about the couple whose grandkids died during the quake.
In episode nine when Mari believes that her daughter and mother are dead. The reunion is heartwarming and sob worthy.
The end of the tenth episode, (Listen, Sis) when it is revealed to Mirai that Yuuki has been dead for the last two episodes.
The final episode, (Dear Yuki) this for both the audience and the characters, particularly when Mirai is finally reunited with her mother and they both embrace each other and sob, both of them in relief for at last seeing each other again and Mirai also in heartbreak as she finally comes out of denial about her little brother's death.
The vase of flowers on Yuki's desk, having seen his classroom in the previous episode.
The credits are both this and Heartwarming. We see minor characters in their lives after the earthquake, including the couple that lost their grandkids in the earthquake sitting together and watching the ocean.