Mike Freeman will remain as director of rugby at the Devon Two club, but Seru, who is also chairman and coach of Plymouth Fijian RFC, will have a key role at Stonehouse Creek.
DHSOB already have 26 Fijian players signed up for the 2016/17 season and they are hoping that could rise.
The Old Boys reached out to the Plymouth Fijian community last season to try and help them get off the foot of Devon Two. They did win three league matches and pick up six bonus points, but they finished bottom of the table after having 25 points docked for errors in registration.
However, DHSOB did reach three cup finals and they are hoping the new campaign will bring more success, especially with the Fijians now firmly settled in at the club.
“We did end last year on a relative high,” said director of rugby Mike Freeeman. “We did reach three cup finals and although we didn’t win them it is something to build on.
“We are looking forward to the new season. There’s a new format for the season with this new cup and that should bring more consistency as teams will be playing every week.”
He added: “We hopefully will have enough players for two sides and what is most exciting is an addition of a colts team again. It is the first time we have had a colts side for a while.”
Meanwhile, Seru’s Plymouth Fijian side will be in action on Saturday when they take on Ivybridge at Cross-in-Hand (2.30pm).
The teams played out a thrilling match last summer, with Ivybridge coming from behind in the dying minutes to win 57-47.
Tomorrow’s match will form part of a family fun day at Ivybridge. The National Three South West side are holding a tag tournament in the morning, starting at 10.45am, which is open to anyone. The final of that will take place at 1.30pm, an hour before the match against Plymouth Fijian.