If you're looking for manga similar to Thumbelina: A Magical Story, you might like these titles.
While on the train one day, Kenji Kaga witnesses the moon splitting into two and then is whisked away to Venor, Earth's sister planet, and informed that both worlds are on the brink of obliteration. Now it's up to the boy to restore order to both Earth and Venor. Alongside the stoic warrior Radein and adorable Pixie, Kenji embarks on an epic quest to find the two sacred objects, and fulfill the ancient prophecy!
The Blue Star Warriors must find a way to infiltrate Uro’s most fiercely guarded headquarters as they fight to save the Pillar of Wind from destruction. They must use all of their resources, including the warship Vleste, now powered by the magical crystal they found in the Lake of Wishes. As Doug is captured by a band of Uro’s soldiers, Naomi and Fly are inadvertently transported back to the planet of Blue Star- revealing the mysterious pathways connecting the galaxies while exposing some of Uro’s weaknesses.
The eldest son of the assassin aristocrat Towerhades. The skill, experience, knowledge of the previous life, magic, all of which grows his power as an assassin. Excellent assassins pass through. He was usually admired as the ideal lord, and behind it wielded a blade as an assassin aristocrat.