Hann had a mistake-free round to win the distance event in 44min 37sec from Tim Robinson (Hutt Valley High School), who finished in 54min 31sec on the course at the Cuttance forestry block, near Henley.
The pair were members of the New Zealand team that finished in the top 10 at the world junior championships in Poland this year.
Robinson made mistakes and lost ground at two of the 20 controls. He lost two minutes on the 12th control and three minutes on the 14th control.
Alistair Richardson (Rudolf Steiner School, Christchurch) was third in 54min 57sec.
The best Otago performance came from Michael Ogle (Otago Boys'), who was fifth in the long-distance event.
The roles were reversed in the sprint race held at the University on Thursday, won by Robinson in 12min 3sec from Hann, second in 12min 23sec.
The senior girls events were dominated by Cosette Saville (Pukekohe High School), who won the long distance race in 59min 53sec and the sprint.
She was nearly two minutes ahead of Renee Beveridge (St Dominic's College, Auckland), who finished in 1hr 1min 51sec. Rebecca Gray (St Cuthbert's, Auckland) was third in 1hr 05min 11sec.
The best Otago performance came from Erin Batchelor (Queen's), who finished 12th.
Malachi Buschl (Outram) won the year 7 and 8 boys sprint race by 25sec in a time of 10min 47sec. He was a close second in the long-distance race in 13min 13sec.
The relay races will be held at Seacliff today.
