Tear Jerker / Hell Teacher Nube

• The chapter/episode with Hiroshi's Missing Mom being reincarnated in a kindergarten girl, Reiko-chan. The last part of the chapter/episode is pure tearjerking of the highest quality in the whole series: Hiroshi rejects his "mom" and runs away since she's treating him like a baby despite being in the body of Reiko-chan, who is at most five years old. His girlfriend Kyouko finds the runaway guy and convinces him to return... yet they find out that Nube had to exorcise Mrs. Tachida's soul from her reincarnation as Reiko-chan, so the child wouldn't be unfairly burdened with memories of her past life. Hiroshi falls to his knees and breaks down in tears, calling out to his mother and telling her that he never meant to be cruel to her and that he misses her so much — then, Reiko-chan channels Mrs. Tachida's soul one last time, so she can properly say goodbye to Hiroshi and let him know she'll be okay in Heaven. When it's all resolved, Reiko-chan's mom comes for her daughter and they go home... and Reiko-chan (who's supposed to not have any memories of this) swears she'll find herself a husband just like Hiroshi, who hears this and smiles.
• The chapter/episode that follows really, really doesn't help Yukime is confronted and completely mindfucked by one of her father's lackeys, the Manipulative Bastard Ippon Datana, who uses only words to completely destroy her self-worth and convinces her to actually harm her love rival Ritsuko if she wants to save her own life. Next thing we know, Yukime has abducted Ritsuko and put her in a Death Trap, all while apologizing and at some point even crying because she has never wanted to go the Murder the Hypotenuse way and knows it's not Ritsuko's fault either, but she feels that cannot do anything to fix it. And for much worse? Once Nube rescues Ritsuko and then goes save Yukime right after having his Love Epiphany about her... He finds her almost dead at the hands of Ippon Datana, having been subjected to lots of literally Cold-Blooded Torture. He carries her to safety, happily telling he about how their life together will be from now on... but misses the exact moment in which she expires from her injuries, only noticing when her body dissolves into snowflakes in his arms, leaving him a screaming wreck. And to finish this pinnacle of sadness, Miki, Hiroshi, Kyouko and Makoto are all sobbing, and Kyouko wonders if Yukime will ever be reborn and have a second chance — and Ritsuko, the same woman whom Yukime attacked in her despair, gently tells her that they should hope so).
• Actually, we were given a massive one already in the second episode (adapted from the third chapter of the second voume). Nube, Hiroshi and Kyouko are trying to deal with an apparently evil "Toilet Hanako" ghost, and a supernatural spirit that might be her slides around and goes through Kyouko for some seconds, which drives her to a crying Heroic BSoD as she can sense its pain... When they find the ghost, it turns out it's not the evil "Toilet Hanako"... but the spirit of a little girl named Hanako who perished in the Tokyo bombings of World War II, trapped in an abandoned house whose spot would later be used to build the school. This drives the kids to tears, but Nube calms them down and uses his cursed hand as well as his sutra to calm Hanako-chan down, then send her to Heaven in peace.
• There's also Ai Shinozaki's Motive Rant, in which she explains Nube and Makoto how come she was possessed by an evil spirit that caused eyes to spread all over her body. It's because she is so lonely and drepressed over being the local Lonely Rich Kid that she developed a shoplifting habit, and the monster chose her as her host due to that. And for worse, she was about to become fully possessed by the monster, and Nube was pressuring her into telling him the reason why without telling her... because the only way to really be freed from that specific monster is to reveal your deepest secrets, the ones that attract it. Thank God everything became better.
• Then there's the Whole Episode Flashback that explains how Minako-sensei died to protect a child Nube from Bakki. Which again brings the sads when Tamamo, Hiroshi and Kyouko Time Travel to help a Nube who's in danger of lose control of his Demon Hand and witness how said Demon Hand was created — and how Nube found out exactly what had happened to Minako-sensei's soul, and then had to fuse her soul with Bakki to both release a possessed little girl and keep Bakki sealed in his hand. The discovery quite shocks Tamamo — and makes both Kyoko and Hiroshi cry buckets.
• One chapter/episode is a Pyrrhic Victory as Nube can only apologize as he seals away a set of delinquents who do not want to be returned to normal as it is the only way he can prevent them from harming others.
• In one chapter of the manga. Hiroshi wins a computer, and when he installs it, an OS with human form named Wlenko appears. The two get along well, and Wlenko develops feelings of love for him. But she has a glitch in her system, and will soon be erased. Therefore, she manipulates Hiroshi to create a cap with circuits and give it to Kyoko, so that she can control her body and be with Hiroshi. He discovers her and break the cap, and when he gets home, he sees that she has little time left to live. Before she died, she wanted to know if she had a soul, so she could be reincarnated and meet Hiroshi again. Nube checks it with his hand, and says that she has one. Wlenko is erased from the computer, thanking Hiroshi for everything and that she hopes to meet him again. But in the end, Kyoko asks him if he told the truth or just lied so she could die happy. Nube does not answer, leaving the question in the air.