Handlung

After failing her first mission, Marinette refuses to become Ladybug ever again, yet Cat Noir can't handle everything on his own, so Marinette has no choice

Adrien decides to disobey his father and goes to high school for the first time. This is when Marinette meets Adrien and thinks that he is no better than Chloé, with whom he is friends. As for him, Adrien will understand that in order to make friends, he would better not take Chloé as a model.

After failing her first mission in capturing her friend Ivan's akuma after he was turned into Stone Heart, Marinette admits to herself and her kwami Tikki, that she is not cut out to be Ladybug, and Cat Noir can't do anything without Ladybug since only she can purify the akumas. When Ivan turns back into Stone Heart, he and his Stone Heart army rise and try to take over Paris, now its up to Marinette to either fight the fight, or walk away.

After failing to purify the akuma, Marinette puts the ladybug miraculous in Alya's bag. Adrien sneaks out of his home and he enters Francois DuPont to attend his first day of school. Chloe starts to ridicule Ivan over his crush on Mylene. Marinette encourages Ivan to admit his love for Mylene and he decides to write a song for her, but he accidentally scares her. Ivan becomes angry and he is akumatized into Stoneheart again. Marinette notices the situation is dire and she takes the ladybug miraculous from Alya's bag and she transforms into Ladybug to help Cat Noir stop Stoneheart and save Mylene and Chloe from the villain. Ladybug is able to save Chloe's life, but Officer Raincomprix blames the hero for her incompetence. Ladybug admits to Cat Noir that it was her fault for not purifying the akuma, but her partner assures her that they will work together to save Paris. Hawk Moth soon introduces himself and he tells the heroes to give themselves up, but Ladybug remains unconvinced over Hawk Moth's words and she warns him that they will find him and take back his miraculous. Ladybug purifies all of the akumas and she assures everyone that she and her new partner will protect the city from Hawk Moth, she releases the purified akumas. Ladybug is able to save Mylene and purify the akuma, with Mylene and Ivan saved, the heroine helps Ivan admit his feelings to Mylene and she looks at his song. Mylene embraces Ivan in gratitude. The next day, Adrien is allowed to go to school. Marinette and Alya decide to reclaim their seats, but Chloe wants the two to sit in front, causing Marinette to stand up to Chloe in front of her classmates. Marinette is still angry at Adrien for the chewing gum incident. When the school day ends, Adrien apologizes to Marinette and he states that he was only trying to remove the gum, he gives Marinette his umbrella and he leaves. Marinette soon develops a crush on Adrien and she heads home. Wayzz praises Master Fu for putting the ladybug and cat miraculous under Marinette and Adrien's care. Master Fu states that those two are made for each other.

Ivan accidentally scares Mylène with his singing. He is turned back into Stoneheart, and his duplicates come to life to serve as his personal army. Marinette tries to pass her Miraculous to Alya, but she is forced to transform back into Ladybug. Hawk Moth demands that Ladybug and Cat Noir surrender their Miraculous, but Ladybug refuses, causing Cat Noir to fall in love with her. That evening, after school, it's raining outside; Adrien shares his umbrella with Marinette, who falls in love with him.