Semper Fi is the nineteenth episode of Gallantmon Strikes.
Johnny offers Charlie to join Murmuxmon & tells him that Murmuxmon]] has educational technology that can give him good grades, but first has to help take out Beelzemon. Charlie refuses Johnny’s offer & transforms. Justimon inserts his Final Vent Card, but Depthmon uses "Attack Vent" (with 4,000 Attack Points) -- summons Mantaraymon & attacks Justimon from behind. Depthmon then escapes.
In Gramercy Park, Lauren calls the bookstore to confront Morgan, but decides she can't do it over the phone & heads on over. Lauren arrives at the bookstore but stops for a moment before entering. She then notices Mako walk past her & enter the bookstore, so she decides to watch through the window. Then Kurt walks in & informs them that Justimon took his father. Then Charlie enters & tells them that he was encountered by Justimon again & that he's running out of time. Mako informs them of the two new Holders, TigerVespamon & Sleipmon. Then Derek & Alan walk in to start a fight in the bookstore. Morgan tells them they need to go somewhere else, they need more room. So they all head into the Digital World to fight. Tom & Lauren see them walk through a window, & also a transformation for the first time as Alan decides to transform before going through the window, which ends up trashing the bookstore. Shocked from what she just saw, Lauren leaves.
Beelzemon, Gallantmon & Depthmon become separated as they enter into the Digital World from different locations. Gallantmon is attacked by a monster. Depthmon & Beelzemon find each other & search for Gallantmon. Gallantmon quickly destroys the monster with his Final Vent, but is then attacked by Sleipmon, using "Spin Vent" (with 2,000 Attack Points). As Gallantmon takes on Sleipmon, he is then also attacked by TigerVespamon. Gallantmon takes down Sleipmon. Beelzemon & Depthmon show up, so TigerVespamon uses "Strike Vent" (with 2,000 Attack Points), & takes them both down. Gallantmon uses Sword Vent & attacks him, & the two run off. Beelzemon & Depthmon try going after them, but Sleipmon gets in their way.
Gallantmon manages to knock TigerVespamon unconscious. Gallantmon takes out his Final Vent Card, but is unable to bring himself to Vent TigerVespamon, so instead just leaves him there while he goes to find Beelzemon & Sleipmon. TigerVespamon regains consciousness.
Sleipmon uses "Attack Vent" (Final Vent) (with 5,000 Attack Points), summoning a herd of Moosemon which attack Beelzemon & Depthmon. The herd vanishes, Sleipmon takes down Beelzemon, & Depthmon is shocked by Justimon's weapon. Gallantmon shows up & tries running to help, but is intercepted by TigerVespamon. Justimon uses Final Vent to use on Beelzemon, but Depthmon gets up & takes the hit for him. Justimon then leaves. Depthmon begins disintegrating & places his right hand over his chest & says, “Semper Fi” (Semper Fidelis: "Always Faithful"). Depthmon is Vented. TigerVespamon & Sleipmon leave. Kurt picks up his Digi-Deck & holds it against his chest & begins to cry, & Mako places his right hand over his chest, in honor of their fallen friend & his sacrifice.