I tried to save someone too but I think it was too late for them. The dark web have tainted their purity.

Your protagonist isn't the first person to want to save or reform someone they love. Its a common theme in stories and it can happen in real life. The would be saviour doesn't always succeed but it shows a good heart if they're trying. They need to be careful not to get dragged down by whoever they want to save, but its an interesting subject for a story,