Director of proceedings Aaron Martin told the tribunal that the nurse had abused his position of trust and taken advantage of Ms NN, the "most vulnerable of patients".
It was the most serious type of misconduct, as he had to know the negative impact that his behaviour would have on Ms NN's health, exposing her to the risk of further harm.
"He knew the patient was at risk of self-harm and suicide. To move immediately into a sexual relationship, her first sexual relationship ... was recklessly dangerous," Mr Martin said.
In the agreed summary of facts, Ms NN was in the nurse's care on several occasions after her admission.
He told Ms NN that he "dreamt about her, that she was meant to be in his life, and that he had a nightmare that [Ms NN] had killed herself".
He started texting her while she was still an inpatient. When she was discharged, he sent her 23 text messages.
They met for coffee twice and they were in constant text contact.
"The texts became increasingly personal and sexual in nature," the summary says.
He later visited her and stayed with her and she made a visit to Hawkes Bay and they had sex for the first time, less than six weeks after her discharge from hospital.
When she returned home, the nurse told her he was under supervision because they had been seen together - but this was a lie to distance himself from her.
When he visited her later, they watched the movie Sucker Punch, during which he referred to Ms NN as "Babydoll" after the movie's lead character.
In the movie, Babydoll is institutionalised by an abusive step-father in an asylum where the girls are trapped and subjected to violence and sexual exploitation. In the final scenes, Babydoll is lobotomised. Around this time, Ms NN tried to kill herself.
In the weeks following, the nurse told Ms NN he was applying for jobs in the city where she lived.
"He spoke about marriage ... and that they would live together."
At some point, the nurse told his supervisor that he felt suicidal, and safer at work than at home. He was advised to take leave, but did not.
In December 2011, the nurse told Ms NN via text that he was being admitted to hospital and had been sectioned on a five-day assessment - but this was also a lie to distance himself from her.
In response, Ms NN had "increased feelings of self-hatred" and blamed herself.
Ten days later, she told someone that her her boyfriend had been her nurse.
When confronted by the Hawke's Bay DHB, the nurse admitted to a sexual relationship.
Ms NN's mother laid a complaint with the Health and Disability Commissioner in January 2012. The nurse lost his job, surrendered his practising certificate, and has not practised since.
He wrote an apology letter to Ms NN and her family after he was investigated.
His counsel, Margaret Barnett-Davidson, said the nurse has accepted that his actions amounted to professional misconduct - though that was a matter for the tribunal to decide.
She questioned the extent to which the relationship had an effect on Ms NN's health.
There was no evidence that "at any point in time her mental health was intensified in its problems, that the risk of suicide was increased" because of the relationship, which was consensual.
She said the nurse believed he was mentally ill with depression at the time of the incident.
Mr Martin asked the tribunal to cancel the nurse's registration - the most severe punishment the tribunal can order - and asked the court to order costs of about $10,000.
"Whether [the nurse]'s conduct is viewed as cynical and predatory, or as extraordinarily poor judgement, he abused a position of high trust for personal and sexual gratification.
"These are not the actions of a nurse who is safe to practice."
Mr Martin said the nurse was aware from the start that the relationship was wrong, but "nevertheless he chose to continue".
Ms Barnett-Davidson said suspension, conditions on returning to practise, and costs of about $5000 were appropriate punishments.
The mitigating circumstances included that it was a consensual relationship, that the nurse was suffering from depression, and that he was not adequately trained at the time they met and should not have been her nurse; he was in his second year as a nurse.
Tribunal chairman David Carden challenged the defence's claim that it was a consensual relationship - not in the criminal sense, but with regard to her mental state.
"I'm asking whether he really understands the vulnerability she had at the time, and how dependent she was on him to discharge his professional obligations properly."
Mr Carden noted that the nurse's apology to Ms NN was at the request of the Health and Disability Commissioner, rather than volunteered.
The nurse faced suspension, a ban and/or a fine of up to $30,000.
