Two years, he thought- two years since I left and everything still seems familiar.
But he knows that this was just an illusion. Mycroft told him that John struggled with depression since he left him without telling him anything. He moved out of their flat and almost dropped out of his studies.
The whole situation weights heavy on his heart and he did not know how he should face John. Sherlock had had a problem, a drug problem and was absent for two years for recovery. To be fair, his brother forced him into the drug rehabilitation and ordered him not to get in contact with John until he was clean. At first he hated Mycroft for this, he denied every phone call from his brother and lashed out wildly if the nurses did not tie him down. After a few months he was calmer eventually and tried to make the best out of this situation. But he really missed John. He wanted to call, he wanted to write letters, but in the end he didn't dare to. And now here he stands, watching John from a distance, not knowing what to do.
John sat at a table and read a book. He looked lost in the large reading room. Two years ago they spent almost every day here, John for his medical studies and Sherlock for his criminology. John was a very good student, not as brilliant as Sherlock of course, but intelligent and Sherlock didn't get bored in his presence.
What he saw didn't seem right; he should be sitting there with him. Maybe he should just go to the table, sit next to John and hope he wouldn't go away. Hopefully he could explain what happened and John would understand and everything will turn out fine. In the moment he decided to go, a blonde girl appeared at John's table and Sherlock's heart skipped a beat. John smiled at the girl and hugged her.
Damn it, he should have thought about this possibility. Why should John wait for him? Sherlock never expressed his feelings for him. Of course he gave no hints and in general he wasn't interested in things like love or relationship. But there was something going on with his brain if it comes to John Watson. And seeing him in the library (their place) with a girl, smiling – Sherlock felt replaced. No, he was not jealous. He was worried about John. Who knows what kind of devil this woman might be?
Maybe he should call Mycroft. His brother knows everyone and everything; he would know who she was and what kind of relationship she and John would have. Nothing worthwhile to stay so he left with a last look at John.
His chest hurts as he left the building. After this unpleasant situation he just wanted to go home. With rapid strides he hurried to King's Cross station and got the Circle Line to Baker Street. What did he expected? John was a good looking young man, almost a doctor and Sherlock was brilliant of course, but also a sociopath and a drug addict. Still after all this time Sherlock didn't know how exactly he became friends with John and why the other man would stick around, even if he was a dick. But after two years of silence it was not surprising that John would move on.
He almost missed his station and jumped out of the tube last minute. Focus Sherlock, he told himself and was angry that something like feelings got him thrown off course. Mycroft would laugh at him if he would know about this. Slowly he walked back to the flat he had shared with John, just as friends of course. Both of them had their own bedroom and respected the privacy of the other one. Mostly.
Sometimes Sherlock 'borrowed' John's laptop. But this was okay, John never complained about this. Sherlock also never mentioned when he found something inappropriate in John's browser history.
He opened the door to number 221b and wasn't even in the house as Mrs Hudson literally jumped at him.

'Sherlock' she cried and hugged him, 'Two years! Where have you been?!'
She looked at him in disbelief.
'Come with me, boy, I have some tea for you.'
And Sherlock couldn't refuse since she immediately dragged him into her kitchen.
'Mrs Hudson, I am really sorry that I just left without a word. It was a hard time for me.'
The old lady looked at him and put her hand on his arm.
'It is okay, Sherlock, your brother told me, no details of course. But you didn't even tell John? You two were such a cute couple.'
Sherlock struggled not to blush.
'We were not a couple, Mrs Hudson. And I couldn't tell anyone, Mycroft had forbid it. I haven't talked to John yet.'
Mrs Hudson sighed and gave him the 'Sherlock-Holmes-you-are-an-idiot'-glare.
'You will call John Watson and apologize, Sherlock. The poor boy, he couldn't even come here and pack his bags. His sister came. You know that he came every day here and waited on the street for you to come home? This stopped a few months ago.'
Mrs Hudson's words weighted heavy on his heart. He felt terrible, how should he apologize to John and how could John ever forgive him? What had he done? He stared in his cup of tea, feeling empty.
'Talk to him, Sherlock' his landlady ordered him to, 'He deserves it.'
He took a sip of the tea before he looked Mrs Hudson in the eye and nodded.
'I know... I promise I will talk to him.'
Sherlock went upstairs in the flat he had shared with John. Everything looked like two years ago.
On second glance however he noticed that Mrs Hudson must have cleaned the apartment not so long ago; a faint smell of her household cleaners reached his nose. And not all of his belongings were in the right place.
Of course… John's sister had been here packing John's stuff. And he was sure that Mycroft swept the whole flat looking for drugs he might have hide somewhere. Slowly he walked to John's room, put the hand on the handle but he hesitated.
What would be behind the door?
A part of him hoped that John would sit at his desk and learning. But the other part knew that John is gone.
He opened the door and seeing the empty room hit him hard. It looked wrong. No books on the desk, no clothes on the chair and no laptop on the bed; just clean white bed linen. Sherlock sat down on John's bed and in this very moment he just hated himself. He hated how that he had been always looking for the next kick, started with drugs, didn't let John help him and letting his best friend down. He had always thought that he was brilliant, better than all other people, superior and now he realised that he was the worst. His selfish behaviour had cost him the trust and friendship of the man he loved.
How could he ever make amends for this?