The book I recommend to you is the System's Ability King. The protagonist was an ordinary office worker who accidentally obtained a special ability system from the future. He mastered a variety of special abilities, such as x-ray vision, latent shadow, penetration, body strengthening, and so on. This special ability system would also alert the protagonist of future dangers so that the protagonist could avoid unexpected situations. I hope you like my recommendation, Mwah ~😗
The characters can be integrated by having them meet in a crossover world. For example, Naruto characters could be transported to the Claymore world and vice versa. They could then exchange their fighting techniques. Naruto characters could teach the Claymores about chakra control, while Claymores could show Naruto characters how to use their yoki - enhanced weapons.