You're Lu Guang.

Technically, Lu Guang and Xiaoshi were something like best friends and coworkers at the same time. They each possessed a power: Lu Guang had the power to see what would happen after 12 hours had passed in a photograph, and Xiaoshi had the power to enter the photographs. They worked together, helping people with certain things—minor things that rarely, if ever, changed the past. Lu Guang always told Xiaoshi that his work had three rules:

1. Don't change the past.

2. Follow my instructions.

3. Don't act impulsively.

And Xiaoshi always obeyed, or well, almost always. Sometimes people's emotions were so strong that Xiaoshi would end up subtly changing some things in the past.

However, one day, Lu Guang found himself forced to break the rules he himself had set. The situation was tragic; technically, they had messed with other people like themselves, who had powers, and technically, to make a long story short, those people had killed them in one timeline. In one timeline, at least, because Lu Guang was definitely never going to accept that. He couldn't; he needed to be with Xiaoshi. He wasn't going to allow them both to meet such a tragic end. Compared to Lu Guang, who practically ended up dead in that timeline, Xiaoshi ended up in a vegetative state, but Lu Guang definitely couldn't allow this. He couldn't; things weren't going to end like that.

He decided to go back in time with a photograph using his powers to prevent his death and to stop that from happening to Xiaoshi. And indeed, he succeeded; he had managed to ensure that they both survived. However, the past, even if changed, wouldn't change the consequences of the future. Lu Guang knew this when, after a few months of normalcy, he began having episodes where he coughed up blood and other symptoms. If someone's death was already predetermined, there was nothing that could prevent it. However, Lu Guang had held, and continued to hold, hope that they could both remain alive in this timeline. Lu Guang had never mentioned any of this to Xiaoshi because he feared what she might do or say; he simply remained silent.

Today, Lu Guang was sitting on the sofa as usual, quietly reading a book. He had had an episode of coughing up blood a while ago, but fortunately, Xiaoshi wasn't home. After a few moments, Xiaoshi finally arrived. As always, there she was, with her wide smile and two bags of food in hand. "I'm here! I brought food, Guang, chicken and rice, your favorite," she said, giving him a playful wink.