補佐官 is read as ほさかん (hosakan) and means aide.
ほさかん
hosakan
だいとうりょうほさかん
presidential aide
だいとうりょうしゅせきほさかん
chief of staff (of US president)
しゅせきほさかん
chief of staff (esp. of US president)
ほさ
aid
ほさにん
assistant
ほさてき
supportive (role)
ほさやく
さかん
field officer
しかんこうほせい
military cadet
かんりほさ
administrative assistant
こくむじかんほ
Assistant Secretary of State
がいこうかんほ
probationary diplomat