With the launch of Valkyria Chronicles 4, SEGA released some free DLC available for download.

Gallian Crest: A “Gallian Crest” decal that can be affixed to Claude’s tank, the Hafen.
Cherub: A “Cherub” decal that can be affixed to Claude’s tank, the Hafen.
Bakery: A “Bakery” decal that can be affixed to Claude’s tank, the Hafen.
Cygnus: A “Cygnus” decal that can be affixed to Claude’s tank, the Hafen.
Royal Flush: A “Royal Flush” decal that can be affixed to Claude’s tank, the Hafen.

The game is then going to receive paid DLC for the remainder of the year. Most of these downloadable content are already included at launch with the Valkyria Chronicles 4 Memoirs from Battle Premium Edition and preorder bonuses. But for the rest of us who did not get the Premium Edition, here are dates you might want to keep track of:

October 09th, 2018: ($6.99) Squad E, to the Beach! add-on that sends the team to the beach.
October 23rd, 2018: ($4.99) A Captainless Squad mission. Already available for free at launch for people who preordered.
November 04th, 2018: ($4.99) Expert Level Skirmishes pack.
November 20th, 2018: ($4.99) The Two Valkyria mission.
December 04th, 2018: ($3.99) Edy’s Advance Ops mission. Already available for free at launch with Valkyria Chronicles 4 Memoirs from Battle Premium Edition.
December 18th, 2018: ($5.99) A United Front with Squad 7 mission. Already available for free at launch with Valkyria Chronicles 4 Memoirs from Battle Premium Edition.

These stories can be played are completing a specific chapter of the main story. To access these stories, go to Book Mode > Menu > Extra Stories.