Daa! Daa! Daa! Season 1 Episode 12 The Mysterious Boy, Yaboshi Seiya

After Kanata and Miyu discover that they are unable to raise Ruu's alien powers with human food, they start trying anything that might work. In the process, they learn that Ruu's powers can help create a plant that responds to the emotions of those around it. Meanwhile, the school has a new transfer student, Yaboshi Seiya, who seems to know a lot more about Ruu and his powers than he should. When Seiya starts following Kanata and Miyu around, they become suspicious of his intentions and set out to investigate.

As they try to uncover Seiya's secrets, they discover that he has a connection to a boy who was once stranded on Earth and helped raise Ruu's ship. However, the boy disappeared under mysterious circumstances and no one knows what became of him. As Kanata and Miyu dig deeper, they begin to suspect that Seiya may actually be the missing boy, using different aliases to keep his identity a secret.

Meanwhile, Ruu's plant continues to grow and becomes a source of amusement for the entire school. However, one day the plant suddenly begins to wither and die, leaving everyone confused and worried. Kanata and Miyu soon realize that someone has been deliberately sabotaging the plant in order to prevent it from revealing their true feelings. As they work to uncover the culprit, they also uncover the truth about Seiya and his connection to Ruu.

The episode ends with Kanata and Miyu confronting Seiya and demanding to know the truth about his identity and intentions. Seiya begrudgingly reveals that he is indeed the missing boy, but refuses to explain why he was hiding. Kanata and Miyu vow to help Seiya and Ruu uncover the truth and solve the mystery of the missing boy together.