He continues to go by "Adam" in situations such as conversations alone with his parents. While he prefers the name, "Ultraman Lightning" is more of a title than anything.
He’s a tourist in a strange foreign country, and wants to see all he can, but won’t let that distract him from his job as guardian of the Earth. When Lightning first came to Earth, he would rather be anywhere else. Initially, Lightning was completely clueless about human life, functions and customs, although he managed to learn the basics from his teammates in CAKE. These negative tendencies tend to die down once he gets used to being around their targets, as clearly shown by the development of his fondness for Earth which began as utter disrespect. When in unfamiliar surroundings or made to do things he doesn't want to do, he tends to act rebelliously or with a superiority complex, demonstrated by his early Earth experience, his first meeting with Geed, and others. In spite of his positives, Lightning has an undeniable jerk streak. He is knowledgeable of the culture of races such as the Dada and Baltan, and can even speak a variety of alien languages. Lightning's main interest is the study of alien worlds, having daydreamed in his youth about protecting fantastical planets as a Space Garrison officer, so one can imagine his chagrin at being assigned to the "plain" Earth. If an alien puts Lightning in a situation that could easily go wrong, he will make it go wrong, as Alien Tilt Vahta and Alien Nackle Versaille learned the hard way. He also has an elaborate sense of humor, finding it particularly funny when enemies are beaten by their own tactics. However, he does not get along with many Ultras of his own generation. He greatly respects Ultras who have defended Earth in the past, considering them his superiors even with his unique powers. Lightning has a soft spot for natural kaiju and won't kill them unless they are truly evil, but flies into a rage when his allies are hurt. Despite his ambition, he is easily distracted, as even small observations can cause his whole train of thought to derail and him to physically mess up. It's sometimes hard to convince Lightning to do things, but once he puts his mind to something, there's no stopping him.
Ultraman Ryusei: Moving Towards the Future