Birmingham are back in the second tier after a one-season absence having romped to the League One last season with a record points tally.
Cashin said the transformation of the club – on the field and off it – backed by their high profile owners was something he wanted to experience.
“You can see in the media, everything that’s going on in the club, and you can see the trajectory and the way it’s going,” he said., external
“That’s something that’s hard not to buy into.
“I know the owners, and the investment has been really good for the club, and I know the manager and his style of play, and the players that have come into the club recently have all been really positive.”
Cashin joins permanent additions Demarai Gray, Bright Osayi-Samuel, Kyogo Furuhashi and Kanya Fujimoto plus loan signings James Beadle and Tommy Doyle in moving to St Andrew’s this summer.
Blues begin their 2025-26 campaign with a home game against Ipswich Town, which is also the curtain raiser for the new Championship season, on Friday, 8 August.