A topic from AEG's L5R CCG Rules forum, copied for Oracle of the Void from a copy of the forum saved in October 2015, so pages it didn't save are missing. Players' names are left out; the rules officials are named. Rulings are as they stood on these dates; later rulings, the rulebooks and the Rules Archive may differ.
The Agasha Join the Phoenix
Choose one family name from another Clan. For the rest of the game, Personalities from that family that you bring (or are bringing) into play are considered members of your Clan. (In Rokugan, a Personality's family name is first).
Hantei Kachiko Scorpion Clan Empress • Experienced 3 Bayushi Kachiko • Unique Reaction: Bow Kachiko to cancel a Limited action.
Is Hantei Kachiko considered a Bayushi as well as a Hantei?
[Mod edit: Thread title. -ZF]
Is Hantei Kachiko considered a Bayushi as well as a Hantei?
No.
http://rules.l5r.com/Legacy_Glossary_F#Family_Name: "A family name is the first (or only) name in a Personality's title" (emphasis added).
The above answer is incorrect. I forgot that the Experienced trait gives a card an alternate title (http://rules.l5r.com/Glossary_E#Experienced).
So the correct answer is yes.