In the fanfic, Naruto could be on a mission where he teams up with Kiba. Maybe they encounter some sort of explosive - laden trap, and Naruto's quick thinking (but a bit miscalculated) actions cause an explosion that involves Kiba. Regarding Issei, if they were to meet in a fan - created scenario, Naruto's unique jutsus and Issei's Boosted Gear powers might interact in a way that causes an explosion. It would be interesting to see how the author would develop the relationships between these characters in such a high - energy, explosive situation.
One possible scenario could be that Naruto, with his shadow clone jutsu, creates a diversion that leads to an accidental explosion involving Kiba and his ninken. As for Issei, perhaps in a crossover setting, Naruto's Rasengan clashes with one of Issei's attacks and causes an explosion. However, this would require a lot of creativity to blend the two very different universes in a believable way.
Naruto could use his explosive - natured jutsus like the Rasengan. If he was sparring with Kiba, a misdirected Rasengan could hit something explosive nearby and cause an explosion involving Kiba. For Issei, if they were in a battle together, Naruto's chakra - infused attacks might react with Issei's energy - based powers in an unexpected way and create an explosion.
Another way to depict the fear is through their internal thoughts. The author could write in the first - person perspective for each character at times. Naruto might think about how the explosions remind him of the destruction he saw during the Pain invasion and how he doesn't want to see that kind of destruction again. Kiba could be thinking about how his ninja skills might not be enough to protect himself and his dog from the explosions. Issei might be having flashbacks to a past experience where he was nearly killed by an explosion and how that fear has now resurfaced.
One possible plotline could be that they are in a village or a world where there is a sudden increase in the use of explosive jutsus or weapons. Naruto, Kiba and Issei have to face their fear as they are constantly under the threat of these explosions. Maybe they start off by trying to avoid areas where explosions are likely to occur. For example, they might stay away from battlefields or places where ninja experiments with explosive substances are taking place. As the story progresses, they could be forced into situations where they have to confront their fear directly, like when their friends or loved ones are in danger in an explosion - ridden area. This would be a great opportunity for character development as they learn to overcome their fear for the sake of others.
One possible reason could be that they had a past traumatic experience related to explosions. Maybe they witnessed an explosion that caused harm to their loved ones or themselves. Another reason might be that explosions in the 'Naruto' world are often associated with powerful and dangerous jutsus or attacks, and they are simply afraid of the destruction and chaos that explosions can bring.
Well, one possibility could be that they are hiding from some sort of danger. Maybe there's a powerful enemy in the Naruto world and in the Issei's world (assuming it's from High School DxD) that they need to avoid. And Risa's place is the only safe haven for the moment. They might be waiting for an opportunity to strike back or for help to arrive.
Another likely antagonist could be a rogue group within Naruto's village. They might have turned against the village's values and see Riasa as a means to an end, like using her as a bargaining chip with other villages or for some personal gain.
Perhaps Naruto has a newfound confidence or a change in his personality that makes Kiba and Issei twitchy. In the fanfic, if Naruto starts acting more recklessly or assertively than usual, it might make them nervous. It could also be that Naruto has some sort of connection to an enemy or a dark force that Kiba and Issei sense, and that's what is making them twitchy.
In this 'Dark Godlike Issei' fanfiction, his personality would also change. He might become more aloof and brooding, as his new power isolates him. He could still have his heroic side, but it would be tempered by his new, darker nature. He might struggle with decisions, not knowing whether to use his power for good or give in to the darker temptations that come with it.
It's a rather unique concept. In the original Naruto series, Naruto is more associated with ninjutsu and his positive, heroic side. Bomb - making is not something that is typically in his repertoire. So in fanfiction, it would be a creative departure from the norm.
Their relationships could develop in a very interesting way. Kiba, being a ninja, might be initially suspicious of Issei's more brash and perverted ways. However, as they are in this situation together under Rias, they start to understand each other better. Issei might learn some discipline from Kiba, and Kiba could become more open - minded because of Issei.