Dirk served as the leader of the Citro Village Defense Corps and was viewed by the other, younger members as something of an elder brother.
However, when his students gained the power of the Mark of the Stars from the Chronicle of the Shining Legacy, Dirk saw his skills quickly become outpaced and found himself feeling unneeded and guilty for resenting their sudden progress. Diadora would take advantage of his feelings, convincing him that the Chronicle was deceiving his friends. He would attempt to set fire to the Company's False Chronicle's before fleeing to join the Order of the One True Way.
After this, Dirk became a librarian of the Order and attempted several times to steal the Chronicles from the Company. Eventually, he would be implanted with the Chronicle of the Furious Roar, enabling him to transform into the Demon Beast Dirk.
Even so, knowing that Valfred was attempting to destroy the Company headquarters through world fusion, he aimed to use his own power to prevent it, throwing off the fusion to a different location. He would trick Liu, taking the Chronicle of the Tatau Council, and challenge the hero to a one-on-one duel, aiming to prove himself with his own strength.
When Valfred began the world fusion to destroy the Company, Dirk was able to interfere with it by the combined power of the two Chronicles he harnessed. He successfully threw off the world fusion to another location and saved the Company. However, the use of all that power would kill Dirk in the process and he passed away peacefully, surrounded by his former brothers-in-arms.
Ironically, as Valfred's plan to wipe out the Company would otherwise have succeeded, if Dirk had not joined the Order, then the Order would have most definitely succeeded in their goals.
- Genso Suikoden Kiwami Encyclopedia, page 749