"Sweet Trap" is the 9th episode of the season "Jigoku Shoujo".
The episode opens up with Hajime Shibata continuing his search for Hell Girl, but gets nowhere and gives up for the day. At a sweetshop, a young woman named Yuka Kasuga talks with the owner. The man, Shinya Morizaki, is a friend of Yuka's late father. She offers some samples of her creations to Morizaki and he informs they are extremely good and says he will sell them under her name, along with her sister's, Hiromi.
Both the girls dream of opening a bakery of their own, just like their father did. They finally get the bakery of their dreams and everything goes on the right track. However, a food critic and her TV show interview both Morizaki and the Kasuga sisters and Yuka shows a creation that is similar to one of Morizaki's. Believing that the Kasuga sisters stole Morizaki's recipes, people start insluting the girls and stop going to their bakery. Yuka enters into Hell Correspondence, wanting to send Morizaki to hell for lying to her and her sister. Ai accepts the request, therefore offering the black straw doll with the red string attached, but Ai warns Yuka of "her end of the bargain". Yuka decides to hold on to the straw doll and confront Morizaki about what he has done. Sadly, the Kasuga's bakeshop goes bankrupt and Hiromi becomes ill, possibly from the difficulty trying to keep it open.
Yuka has had enough and sneaks into a party where Morizaki is at. Yuka confronts Morizaki in an empty hallway and asks why he stole her creations. Morizaki tries to send her away, but he later admits that he was in love with Hiromi, but he became angry when Hiromi refused to marry him. Yuka is shocked and takes out the black straw doll, saying "this is for you, Hiromi" and pulls the string. The doll disappears and Wanyudo's voice replies, "Your grievance shall be avenged!" At Ai's place, the Hell Girl prepares for her mission and goes after Morizaki. Tsugumi sees the party through a vision and informs her father about Morizaki's fate and he runs to the building.
First, the partygoers taste some of Morizaki's cakes, but they claim they taste awful and they throw the cakes at Morizaki. Then, Hone, Ren, and Wanyudo, playing as interviewers ask if Morizaki really stole Kasuga's recipes for revenge. Morizaki runs out into the hallway, where he finds Hiromi. Hiromi throws her arms around him and says, "If you love me, than eat me." Suddenly, she becomes icing, and Morizaki runs away in terror. He runs into a taxi, where Wanyudo is waiting and he too becomes icing and traps Morizaki. He wakes up in a black space, with pastries floating around, where Hone, Ren, and Wanyudo ask if Morizaki will confess his sins, but he refuses, saying that it was Hiromi's fault for refusing his proposal. Hone than calls for her mistress and Ai appears and delivers her speech, "Perhaps, it is time to die." Morizaki awakes to find himself on Ai's boat, with Hone disguised as Hiromi and she sticks a bony hand into his mouth, as they ferry him to Hell. Later at the party, everyone is worried that Morizaki didn't show up at the interview and several partygoers go looking for him. Hajime arrives too late to save Morizaki.
Some time later, Hiromi is seen working at a local bakery, trying to save up again and buy back the dream bakeshop. Yuka is happy that her sister is well again and she runs off to her job and the camera shows the black fire symbol on her chest.
The ending shows a candle, with Yuka Kasuga's name on it, being lit, and Ai's voice is heard, "Your grievance shall be avenged."