Definitely not a happy ending. The manga takes some dark turns and doesn't wrap up in a traditional cheerful way. It's more thought-provoking and emotionally charged than just happy.
I'd say it's good. The manga has a complex and engaging storyline that keeps you hooked. The art style is also distinctive and adds to the appeal. But be prepared for some intense and emotional moments.
One way is to create a common threat. For example, a new powerful enemy that neither Naruto's ninja world nor Lucy's world can handle alone. This forces them to team up. Another way is through a portal or some kind of magical/scientific accident that brings them together. Then, the story can unfold as they learn about each other's powers and worlds.
Lucy is a very important character. She is a Diclonius with a tragic past. Her powers are both a curse and a means of survival. Kouta is also important. He has a connection to Lucy's past and his kindness towards her, despite her nature, is a key part of the story. Nana, another Diclonius, plays a significant role as well. She has her own journey of self - discovery and her relationship with the other characters is complex.
One of the main themes is the exploration of human nature. The story delves into the darker aspects of humanity, such as prejudice and fear. Another theme is isolation. The characters, especially the Diclonius like Lucy, are often isolated due to their differences. It also touches on the theme of redemption. Some characters strive to overcome their past mistakes and find a way to be redeemed in the eyes of others and themselves.
One common theme is the exploration of the characters' powers in new and combined situations. Since both Naruto and Elfen Lied have characters with unique abilities, fanfiction often delves into how these powers would interact if the characters were in the same universe.
The story of Elfen Lied is centered around Lucy. As a Diclonius, she has a tragic past. She was experimented on in a facility. Her escape sets off a chain of events. In the outside world, she is a very dangerous being due to her vectors which can cause great destruction. But beneath her violent exterior, she has a more complex personality. She meets Kouta and his friends. Kouta's family once took care of Lucy when she was a child, which adds an emotional depth to their relationship. The anime also delves into the ethics of the research being done on Diclonius. It shows how society reacts to a being that is different and feared. There are many sub - plots and character developments that make the story engaging and thought - provoking.