In act 34, a beautiful white pegasus came to Chibi Usa in Ichinohashi park, where she, Usagi, and Mamoru stood, watching the solar eclipse. He looked at Chibi Usa, and called out to her, saying, "Maiden." Later, he appeared in her dream, where he took her for a ride on his back and told her that he needed her help to save Elysion. He didn't explain where or what Elysion was, only that his name was Helios, and he needed her to lend him the power of her beautiful dreams to save Elysion. He gave her a bell, and told her to use it to call him, and he would lend her his power when she needed him. When she does need him later on, fighting the Amazoness Quartet's lemures, he tells her to use the bell, and she calls "Helios! Please! A weapon for us! Please! Twinkle Yell!" This summons him, and he comes and attacks the lemures.
Chibi Usa's next encounter with Helios is in her bedroom, after Palla Palla switched Chibi's and Usagi's ages. He sees her, and tells her that she is beautiful, then tells her that only she has the key (her beautiful dream) to unlock his cage (the golden crystal), and only the princess of the white moon can do it. Then, near the end of act 35, Super Sailorchibimoon (finally in her correct body) summons him, and tells him that she is not the maiden he is looking for. Hearing this apparently confuses him a bit, but he fades off as she runs away. He finds her, shows her his true form, then kisses her, telling her he will meet her again, before disappearing.
During the final battle, Helios helps Sailormoon, and Tuxedo Kamen, and reveals things about Elysion, the Moon Kingdom, and the two Maenads who protect Elysion. The story of the maidens, and the power, and it shows that Small Lady Serenity is Princess Lady Serenity, the maiden whose power protects the land. Later, when Sailorchibimoon revives Helios at the end, he sees her as Lady Serenity, and realizes that she is the maiden he had been searching for. He promises to see her again someday, when she becomes Lady Serenity, and she vows to work toward become that Lady, and a soldier on her own. It truly is a twilight romance.