Eddie Howe's side broke the deadlock in the opening minutes of an eventful first-half at the Saitama Stadium in Japan courtesy of Alexander Isak's clinical finish before Rio Nitta levelled the scoring for the J. League outfit.
After Newcastle goalkeeper Nick Pope saved Atsuki Ito's penalty, Murphy fired United ahead on the stroke of half-time before the winger's curling effort two minutes after the restart doubled the Magpies' advantage.
Lewis Hall's long-range effort shortly after the hour mark rounded off the scoring as United continued their 100 per cent winning start to pre-season.
In the third minute, Isak opened for the Magpies as the Swedish frontman latched onto Joe Willock's pass and, despite losing control of the ball following a darting run, managed to quickly regain possession on the edge of the box before firing a low effort into the bottom left-hand corner.
Harvey Barnes went close to doubling United's advantage shortly after Isak capitalised on a defensive mix-up between Rikito Inoue and goalkeeper Ayumi Niekawa but Barnes' goal bound effort was blocked by the Japanese defender.
In the 23rd minute, Newcastle found themselves back on level terms as Nitta levelled the scoring for the Red Devils, guiding the ball into the net from close-range via the right-hand post following Yusuke Matsuo's cross.
Newcastle conceded a penalty before the half-hour mark as Hirokazu Ishihara was tripped by Tino Livramento, despite the incident arguably taking place outside of the box, but Pope denied Ito from 12 yards, guessing the correct way to block the midfielder's powerful spot-kick before Tomoaki Okubo's resulting cross-cum shot was cleared to safety.
Pope then produced a splendid one-hand stop to deny Nitta, pushing away the winger's stinging drive before Okubo flashed a low effort wide of the right-hand post.
Murphy continued his bright goalscoring form in pre-season after regaining Newcastle's one-goal cushion on the stroke of half-time. After Willock won possession before completing a positive run towards goal, the midfielder teed up Murphy who drilled a first-time effort into the net.
In the 47th minute, Murphy extended Newcastle's lead further after collecting Jamie Miley's pass, introduced to the field at the restart, before curling the ball into the bottom left-hand corner.
Pope prevented the Reds from narrowing the deficit shortly after, parrying Ryoma Watanabe's initial strike before bravely blocking Thiago Santana's rebound whilst situated on the ground.
In the 59th minute, Hall added gloss to the scoreline as the teenage left-back controlled Murphy's pass before his strike from distance flew into the right-hand corner via Yota Sato's deflection.
Newcastle will face last season's J1 League runners-up Yokohama F. Marinos on Saturday, 3rd August at the Japan National Stadium in Tokyo (kick-off 11am BST).
Newcastle United: Nick Pope (Odysseas Vlachodimos 62), Tino Livramento (Alfie Harrison 71), Emil Krafth, Dan Burn (c) (Cathal Heffernan 79), Lewis Hall, Sean Longstaff (Jamie Miley 46), Joe Willock (Miguel Almirón 46), Joelinton, Jacob Murphy (Jay Turner-Cooke 71), Harvey Barnes (Trevan Sanusi 62), Alexander Isak (Ben Parkinson 62).
Subs not used: John Ruddy.
