Ben Wright suffered a fatal heroin overdose in Hove after purchasing illicit substances off the internet.
The 22-year-old was found at his home in Lansdowne Place, along with packages of ketamine and cocaine.
His heartbroken father Duncan broke down as he listened to the evidence of his son’s death, telling the inquest: “This was not the Ben I knew.”
A hearing at Hove Cricket Ground was told that police found a “drugs diary,” documenting the illegal highs that Ben had taken since the start of the year.
Investigator Andy Boyd said: “In the diary, he was recording his drug use.
“The diary showed police that he had been purchasing drugs on the internet, in what is commonly known as the dark web.”
Ben was discovered by paramedics at his home and pronounced dead at 5.30pm on February 11. He was identified by his flatmate.
Tuesday’s inquest heard how Ben’s flatmates were aware of his drug use but not the extent as it was “effectively taking place behind closed doors”.
Police found brown cardboard boxes in his room containing packages of powder, including cocaine at 60 per cent purity, as well as over-the-counter medication.
Toxicology reports showed the provisional cause of death was heroin and dihydrocodeine toxicity with the presence of benzodiazepines.
Police were satisfied there were no suspicious circumstances but could not confirm where or how the heroin had been purchased.
Officers had seized a laptop and mobile phone belonging to Ben – but they did not have the pin code.
The inquest was told that without the pin it could take between three months and 21 years to access information relating to the purchase of any drugs from the internet.
A bank account linked to Ben was also discovered, with officers continuing to investigate his most recent online purchases.
Assistant coroner Sarah Clarke said she was satisfied Ben’s death had been as a result of “misadventure”.
She paid tribute to his parents, saying: “It is not right that you should be here.
“Ben was at university, had a girlfriend, and was doing all the things a 22-year-old should be doing.”
Recording a narrative conclusion, Mrs Clarke said that, on the balance of probabilities, taking the drugs had been a deliberate act.
She said Ben had been “reckless” but that she was satisfied he was not aware of the consequences.
“I have heard evidence that Ben was compassionate and a deep thinker,” she said.
Ben’s father, Duncan Wright, addressed the court, thanking Sussex Police for their investigation
After the inquest, Ben’s neighbours spoke of their shock at the circumstances of his death.
One neighbour told The Argus: “I didn’t know those who lived there but I don’t think anyone is living there anymore.”
Another neighbour who lived upstairs from the property where Ben lived also said he was unaware of who had been living in the flat.
“I don’t want to answer any more questions,” he said.