- "The rain sure nice, isn't it? it brings back old memories."
– Gole's opinion about the rainy weather.
The episode is followed up by The Mush Sisters are Shy.
On a rainy day, Sumire finds a mysterious letter in the library. So she suggests to her Fairilu friends that they go out into the rain to find out about this letter.
Out in the rain, Nozomu tries to meet a Fairilu by opening a Fairilu Door in various ways, but is unable to. He thinks Fairilus may not like the rain and decides to try again later. The rain stops shortly and Nozomu looks up at a rainbow in the sky.
In the cafeteria, Lip and Himawari recently finish their homework with Omatsu. Relaxing, Himawari becomes dismayed that she can't play outside due to the rain. Then she sees Weather Fairilus Sun and Amemi. She comes up to Sun and asks him to use his Fairilu Magic to stop the rain. He says he couldn't, but Himawari begs him. The two decides to cheer Himawari up by using their sequential magic to make Amemi's rain clouds appear then cleared away by Sun's sun. The two explained that they needed the rain and that even the two can't change the weather.
Later, Sumire comes up to Lip and Himawari and tells them they would like to go for a walk in the rain. But the two says they will get wet when they go out. So, Sumire uses her magic to give the three of them rain gears. Prepared for the rain, the three go outside and have fun playing around in the rain.
The three continue walking and Lip wonders how much longer they are going to walk. Himawari starts to become bored, in the process she frequently gets buffeted by the harsh windy weather. Eventually, Himawari becomes angry and wants to go home. At loss for words, Sumire feels guilty for letting her down; the two end up in tears.
Lip starts to feel bad for them and wonders what to do now. Then her key begins to glow. Getting an idea, Lip uses her magic to make the rain fun. The result was a sound of music melodies coming from the rain and Lip begins to have fun. Himawari and Sumire eventually regains their happiness and start dancing along with Lip.
Then, the rain stops and the sun appears. The three continue their journey and they come across a visual display of a series of rainbows in the sky, in which Sumire calls it the "Rainbow Bridge". She explained that it appears every time the rain stops and that the place they are at is the only place in Little Fairilu they can see the Rainbow Bridge. She wanted to share this with the two, but was unreasonable in the process and feels sorry for doubting them. Seeing how Sumire really wanted this for her friends, Himawari bursts into tears and feels very sorry for doubting her. The two accept their apologies.
Lip asks how Sumire knew about the Rainbow Bridge. She explained that she found an old letter in one of the books in the library. The letter itself appears to be an unsigned love letter about the rainbow bridge. Lip imagines that the writer saw the rainbow with the person she/he truly loved, just like the three saw together. Lip and Himawari thank Sumire for sharing the great experience together as friends.
Meanwhile, Marje was seeing them and becomes surprised to see that Sumire has the letter revealed to have belonging to her, leaving her very embarrassed. Gole, also aware of the letter and the three's adventure, playfully comments the 'memories' they've shared together in the rain just like the three did. Her face turning red, she takes some books and changes the subject to prepare for lesson plans and leaves, only to be unaware that another letter falls from her books. Lip, Himawari, and Sumire head out; Himawari comments she had begun to like the rain now and Lip suggest that they should go see the Rainbow Bridge again when it rains again.