In a futuristic world, the virtual world is merely a layer on top of reality; within it, cyberpets are abundant and information is plentiful, and it is only visible by wearing special cyberglasses. In Daikoku City, this cyberspace is behaving strangely: cyberpets are going missing, dark entities known as "the Illegal" roam obsolete space that shouldn’t exist, and a large pink antivirus program known as Satchii wanders the streets, attacking both virus and pets alike. Sixth grader Yuko Okonogi has just moved to Daikoku City, and after cyberdetective children help her rescue her lost dog, she soon joins the others in a search for the truth behind these strange occurances.
In the sixteenth century, Esteban is a Spanish orphan who travels the seas with Mendoza - the man who saved him from dying in the midst of a storm, when Esteban was just a child. With Esteban in tow, Mendoza has set forth to the new world in search of the Mysterious Cities of Gold and riches beyond his wildest dreams - but all Esteban really wants is to search for the location of his father. The duo is also joined by the Incan girl Zia, as only she can translate the writings that will help lead them to the treasure. Mendoza, while seemingly caring, has ambiguous motives; though the intentions of Commander Gomez and Captain Gaspard are clear: find all of the gold that they can, and step on anyone that gets in their way...
In both Mysterious Cities of Gold and Denno Coil, the protagonists (Esteban and Yuko) are initially portrayed as lonely characters unaware of the marvels of the greater world around them. But soon they will form a close friendship with other children, and thus the young group begins an adventure together into the unknown.
Esteban and Yuko also possess a hidden skill or power that is quite unique to them, but of course they have no idea how to use it at first and know only that they feel different to other children of their age. The children in both stories are faced with mysteries, technological wonders, strange beings, countless challenges, and many dangers, as well as being guided by figures whose true intentions are a closely guarded secret.
Naruto Uzumaki is a young ninja who bears a great power hidden inside him, a power that has isolated him from the rest of his village. As such, his only dream is to become the Hokage - the most powerful ninja, and leader of the village; but first he needs to graduate! With his inability to perform even the most basic ninja techniques, it seems that all Naruto has going for him is his determination to succeed no matter what. Teamed up with the genius Sasuke, book-smart Sakura, and their team leader Kakashi, Naruto embarks on his quest to become the Hokage. But with outside forces posing a threat to the entire Hidden Leaf village, Naruto discovers that he must become much stronger if he ever wants to realize his dream and protect the friendships he's forged.
There are some things that can only be said after death. Aided by a talking staff that thinks it is alive, Fumika delivers Shigofumi, the last words and feelings of the dead in the form of letters, to their addressees. Whether they are letters of apology, revenge, or simply a final farewell, she always brings them to their destination. Delivering Shigofumi is not always an easy job; as some people refuse to believe such things as letters from the dead are possible, while others are afraid of what these letters might contain. But the mail must go through; what the recipients decide to do with it afterwards is up to them.
Aizawa Ayumu is spending the summer visiting his father in the quiet, rural town of Tana; but before long, he begins to notice that things aren't quite right. Flowers are blooming out of season and stories of ghosts and kappa abound, but for Ayumu, the strangest thing of all is the appearance of mysterious creatures who take the form of floating balls of light. Adding to this mystery is Wakkun - a boy who seems to be connected to the lights and claims to know Ayumu from the past. Now, Ayumu begins to search for the truth about the lights and Wakkun, as a summer like no other begins...
In both series we have a pack of friends with their little problems and quirks. Both series have lovely slices-of-life part which is not so common in anime, so instead of watching another seventy thousand rockets being hurled at an enemy in a badass giant robot we can see how children interact with each other, gradually grow up and form bonds, now isn't that epic ? :-)
Finally both series have the mystery part to them, each plot being interesting and dealing with rather serious stuff (no REAL viiolence though which is good too for a change).
All in all if you liked one then the other won't disappoint you.