Short answers, pulled from the story.
Daisuke Watanabe wrote the dialogue for the Zanarkand Ruins in Final Fantasy X in 2001. This task required him to complete an entire section of the game in a single night under immense pressure. The experience marked his first major contribution to the Final Fantasy series.
Daisuke Watanabe joined the Final Fantasy XII development team in November 2004 after original scenario writer Yasumi Matsuno left due to sickness. He worked on the project until about March 2006 when he rejoined the Final Fantasy XIII team. Co-director Hiroshi Minagawa expressed regret that many of Watanabe's story ideas had to be dropped to meet the release deadline.
Daisuke Watanabe began writing for the Kingdom Hearts series in 2002 and contributed to the original game. He worked on Kingdom Hearts: Chain of Memories in 2004, Kingdom Hearts II in 2005, Kingdom Hearts Re:Chain of Memories in 2007, and Kingdom Hearts 358/2 Days in 2009. He served as scenario text planner for the 2005 title and as scenario supervisor for the 2009 title.
Daisuke Watanabe published a three-part novella titled Final Fantasy XIII Reminiscence: tracer of memories. The novella was released in the Japanese game magazine Famitsu to provide additional context to the events of Final Fantasy XIII. Fans received the project well for offering deeper understanding of the characters and their motivations.
Daisuke Watanabe served as scenario advisor for Final Fantasy XII: The Zodiac Age in 2017. This role continued his contributions to the Final Fantasy franchise in his later years. His work on the project solidified his reputation as a writer who could handle complex narratives with ease.