Invisible Advertising: A major problem that is facing the series, second to Late Export for You. Outside of Japan in which it sells steadily, the series suffers from little to no recognition in the global gaming community, despite the series being more than a decade old. Being constantly overshadowed by other JRPG series like Final Fantasy and Persona really isn't helping. Even when it comes down to Falcom's own advertising, the Ys series is often given preferential treatment over the Trails series.
Late Export for You: While Falcom is on record stating that they'd like to see the Crossbell games marketed outside of Japan, it's never been economically feasible: Due to the enormous amount of text in these games, translating them is time-consuming and expensive, and since the Crossbell games are console only and each version has invariably only been released towards the end of the supporting console's expected lifespan, by the time the games would be ready to sell, the market would be fading, making the effort very financially risky for any localization company. However, this changed as the Crossbell series were ported to the PS4 in 2020, which combined with NIS America's promises, made fans hopeful that the game would at least be released worldwide this time around - especially since, even though the PS4 is also reaching the end of its lifespan, Sony has engineered the PS5 to be backwards compatible with the PS4, making games on the older platform financially viable for longer. Both games would finally got an official release overseas in 2022 and 2023.
NIS America's localization for the Crossbell games only subtitled it using the script they acquired from Geofront, with no English dub in place.
The Chinese and Korean translations keep the audio in Japanese, largely due to their very fast turnover rates. It's not uncommon to see a localized Trails game in Chinese less than six months after release in Japan.
Sleeper Hit: A defining example in the west. The series was little more than a niche cult hit in its early years, struggling to find enough success to break even on the dying PlayStation Portable. After a protracted period of Development Hell getting the Sky games localized, the games quickly gained small but steady word of mouth praise, for its sprawling, interconnected stories and Worldbuilding. The series got a big shot in the arm with the release of the Cold Steel games on PC and PS4.
Throw It In!: According toWord of God, characters in the in-game books weren't actually supposed to appear in later games themselves. An example would be Ein, the 1st Dominion herself as she was supposed to be someone very different (appearing as Toval's partner). In fact, Kondo claims that whoever gets newly hired as a writer in their staff would write the in-game books and just have it as a fictional character. It was only when Ein existed that the trend started to happen where the books are actually a Fiction as Cover-Up for the real person in-game.
Out of Order: The localization has suffered a little from this since the release of Trails in the Sky SC, following which Trails of Cold Steel I and II were localized while skipping Trails in the Sky the 3rd and the Crossbell arc entirely. While Trails in the Sky the 3rd was eventually released in English in 2017, the Crossbell arc, made up of Trails from Zero and Trails to Azure, remained officially unlocalized until 2022 and 2023, with Cold Steel III and IV having already been localized in the interim.
What Could Have Been: If the poster in Tokyo Xanadu has any truths to it, apparently Falcom was at one point considering making a sequel of Ys vs. Sora no Kiseki: Alternative Saga, called Ys vs. Sen no Kiseki II: Another Chronicle. note According to this article, Kondo said the mockup poster was included in the game to see if people would start pestering them to make it happen as there is a group of devs in Falcom who wanted to make the sequel, but they needed to gauge the public's interest first to make sure it's worth the time and effort.
Word of God, characters in the in-game books weren't actually supposed to appear in later games themselves. An example would be Ein, the 1st Dominion herself as she was supposed to be someone very different (appearing as Toval's partner). In fact, Kondo claims that whoever gets newly hired as a writer in their staff would write the in-game books and just have it as a fictional character. It was only when Ein existed that the trend started to happen where the books are actually a Fiction as Cover-Up for the real person in-game.