"Love is bitter-sweet" is the twelfth and final episode of the second season of the anime Sekai-ichi Hatsukoi. The episode revolves around the couple Ritsu Onodera and Masamune Takano. This episode mainly resolves around Takano's past and how he became the person he is today.
The scene starts off with Takano and Ritsu on a busy train. Ritsu asks Takano why he was standing right next to him since he was sitting. Takano tells him how there is nowhere else to sit besides, and then says how he'd like to sit beside him, using his cold as an excuse. A lady gets off and Ritsu orders Takano to sit there instead. Takano says he will. He then thinks about, despite the basis of his personality staying the same, how much Ritsu has changed since their high school years. He recalls how easily flustered and outspoken he had been. Still exhausted from his cold, Takano falls asleep and has a dream about his high school year.
Ritsu tells Saga that he loves him. Saga knew who he was even before the day he confessed to Saga. It's Saga's third year of high school and he has college plans to think of. A meeting for all students were ordered to come with a parent. A girl comes to Saga and asks if she can borrow his history notes because she was absent. While blushing, she tells Saga that she knows that he writes good notes. Saga lends his notebook to the girl, who promptly runs to her two friends telling her good job.
Saga looks up at the clock and notice it's four. He would normally kill time by going to the library since he knows that his parents would be home. Saga opens the doors to the library to find Ritsu sitting at a desk. Saga goes up and asks him if he was going home and Ritsu says he was about to leave. Ritsu stops Saga from walking asking about what happened the other day when he asked Saga to go out on a date asking if it was a joke. Saga thinks that, while it wasn't a joke, it wasn't serious either. Saga had known that Ritsu has feelings for him. This due to Saga re-reading the books he read and only to find "Oda Ritsu" on every check out slip. He never thought someone would read a book that looked boring and came to the conclusion that Ritsu must like him.
Saga goes home and is greeted by Sorata, (who is a kitten during this time). He opens a door finding his father. His father coldly asks him where he was and if he was hanging out with people. He tells him that high-schoolers aren't supposed to act like that, which makes Saga think to himself, "What a nice way to welcome someone back home". His mother asks where he found the cat while Saga simply replies that he found it. His mother tells him that she hates animals. Strangely Saga's parents are facing behind each other. Saga's father tells Saga that he left some paperwork in the house only finding Saga's mother inside as well. Saga explains that his father is a surgeon and his mother is a lawyer. While they look like they are a wealthy good family, they are actually not a good or loving family. Every time his father and mother were in the same place at the same time, they argue and fight. Saga tells his parents that the meeting for high school graduates were going to begin and asked if one of them can come. Saga's dad coldly replies that he can't and make his mother go. His mother says the same thing and tells Saga to choose what college he wants. His mother leaves him with money for the house and food for Saga. Saga doesn't say anything and leaves the room.
Sorata is sitting on top of Saga's belly while Saga is looking up in the ceiling. Saga picks up Sorata and curls thinking about an ex-girlfriend whom he broke up with due to her wanting a serious and exclusive relationship - causing him to lose interested. He then wonders what it would be like to date a guy, gradually turning his thoughts in wonder about what sex between two guys would be like. He then suddenly stops his train of thought.
Saga is going to the bookstore of a new manga when he sees Ritsu standing in front of a fast food restaurant (similar to Subway). A lady asks many questions about what he wants on his sandwich. Ritsu is clearly uncomfortable being asked so many questions like what type of bread, sauce, meat, etc, while Saga stares at him. Ritsu ends up getting the same thing that Saga gets. Ritsu tells Saga that he is sorry and Saga tells him it's alright. Ritsu explains that it's his first time eating at a fast food restaurant since his friends always bought their lunch from the restaurant. This made him want try it himself, but he was intimidated by the order and the long line. Ritsu tastes the sandwich, saying it's delicious. Saga asked if he never eats fast food and Ritsu says that his parents dislike that kind of stuff. He also has never had any pre-made food. Ritsu tells Saga that he is glad he came with him for lunch.
Saga comes home once again greeted by Sorata. His mother comes out of the door giving Saga his post high school conference sheet which makes Saga ask her if she is coming. His question was interrupted when his father leaves the room making his mother ask what he was doing.
Saga's mom ends up not showing up in the meeting but tells him that he can choose his college. Saga tells his teacher that they don't know what college they want him to get into and they won't be interested in it anyway. Saga leaves passing by the brunette girl from before. She asked Saga if he was going home, only getting a no for an answer. Saga makes his way to the library finding Ritsu. Ritsu tries to talk to him and shows him a manga but Saga takes his frustration out on Ritsu and tells him if Ritsu was saying he loved Saga, he should have talked to him more often. Saga cools down telling him that he wants to be alone for now. Ritsu leaves the library. When he leaves he sees that Ritsu came back with a umbrella because it was raining outside and he didn't think Saga had one.
The next day, Saga is confronted by the brunette girl. She confesses her feelings to Saga but Saga says no. She later asks him if he was already in love with someone else. Saga replies with a yes.