expression, suru verb (irregular)
have an ulterior motive; have an axe to grind
Used when someone's actions are not straightforward but driven by a hidden personal agenda. Often used in negative or suspicious contexts.
彼の親切はためにしているとしか思えない。
I can't help thinking his kindness has an ulterior motive.
あの
That politician's remarks must have an axe to grind.