The "Magnum P.I." reference in this episode raises the intriguing multiple cross-over paradox that within the "new" Hawaii Five-O story-universe, the original Tom Selleck version of "Magnum P.I." actually exists possibly as an in-universe tv series fictionalised dramatisation of Robin Master's line of books, which the "new" Hawaii Five-O team are obviously fans of. Considering that original Magnum was considered a spin-off of original Hawaii-Five-O, and the later "re-boot" of "new" Magnum share the story universe with this new version of "Hawaii Five-O", as well as other CBS series, as at october 2019, there has been no in-universe explanation, although remember that "new" Magnum didn't start until several years after this episode.
Max compares Steve and Danny to characters from Magnum PI. In its first season Magnum PI was treated as a spin off from original Hawaii 5-0 with several references to the original Steve McGarrett
At the end of the episode Max is likening Steve to Magnum PI. He suggests that this would mean Danny is 'Rick'. In a previous episode, Larry Manetti who played Orville 'Rick' Wright appeared as Nicky 'The Kid' Demarco.
Near the end of the episode, Max, Steve, Danny, and Kamekona discuss Magnum PI, comparing themselves and each other to characters on the show and humming the theme tune. Magnum PI was later rebooted and is set in the same universe as this show, with Kamekona appearing briefly in the second episode of season one ("From the Head Down").
Title translates to 'close friend' per Netflix