The biggest obstacle would be their conflicting ideologies. Naruto believes in the power of friendship and forgiveness to bring peace, while Pain believes in using force and instilling fear. It would be very difficult for them to overcome this fundamental difference in their worldviews and come together in love.
There is also the matter of their past actions. Pain has caused a great deal of destruction and death in Konoha, which Naruto loves deeply. Naruto's friends and comrades would likely be very opposed to any kind of relationship between Naruto and Pain. This social and emotional pressure would be a major obstacle.
In a more modern - day fanfic, their own insecurities could be an obstacle. Rin might be insecure about her looks compared to other girls around Len, or Len might be worried that he's not good enough for Rin because she's so talented in music or art. These insecurities could lead to arguments and strain on their relationship.
One possible obstacle could be his own laziness. He might find it difficult to put in the effort required in a relationship, like going on dates or buying gifts. Another obstacle could be his loyalty to the village. His duties as a ninja might take him away from his loved one for long periods of time.
One possible obstacle is family acceptance. Many transgender people struggle with getting their families to accept their identity and their relationship, which can put a strain on the love story.
One possible obstacle could be the constant battles against villains. The ninjas are always in danger, and it's hard to focus on a relationship when you have to fight for the safety of Ninjago all the time. For example, if two ninjas are in love, they might be separated during battles or one might get injured, which can put a strain on their relationship.
One obstacle could be the dangerous nature of their jobs. They are constantly facing threats from criminals, which could put their relationship at risk. For example, a criminal might target their loved one to get back at them.
One possible obstacle could be the difference in their habitats. Robin might prefer more open and sunny areas, while Raven could be more at home in darker, more secluded places. Another obstacle could be their different diets. If they can't find a common food source, it might cause problems in their relationship.
One obstacle could be their different village loyalties. Naruto is from Konoha and Temari is from Suna. Their villages may have different interests at times, which could put a strain on their relationship. For example, if there are disputes over resources or political matters, they might be on opposite sides.
One way to conceptualize a love story between Naruto and Pain could be through the idea of redemption. Naruto might see the pain and confusion in Pain's heart that led him to his extreme actions. He could strive to show Pain a different path, and in this process, a deep connection could form that might turn into love. Naruto's unwavering belief in the goodness of people could gradually break down Pain's walls.
One possible plot is that Pain targets Hinata to get to Naruto. Since Hinata has a special place in Naruto's heart, Pain might think that by hurting her, he can break Naruto. But Hinata shows great courage and Naruto comes to her rescue.
The differences in their personalities could pose as obstacles. Kick is impulsive and often acts without thinking, while Kendall seems more level - headed. This could lead to clashes. For instance, Kick might plan a dangerous stunt without considering Kendall's concerns. Also, their age and maturity levels might play a part. If Kick is not ready to settle into a relationship because he's too focused on his stunts and having fun, it could cause problems in their relationship. And Kendall might be looking for something more stable and committed, which could create a rift between them.