It is said that the motive that Shinsengumi assassinated Uchiyama was as follows: Uchiyama was suspected of having cooperated with Onogawa-beya (a sumo stable) in the 'Osaka sumo wrestling incident' that a scuffle occurred between Shinsengumi and sumo wrestlers of Onogawa-beya when Shinsengumi went to Osaka for a business trip in the year before; or the investigation of the incident was aggressive and it caused a feud between Uchiyama and Kondo and then Kondo had a grudge against Uchiyama; or Uchiyama was suspected of having driven up rice price and oil price in conspiracy with supporters of tobakuha (anti-bakufu, crushing-the-bakufu faction) and inflicted a well-deserved punishment on him.
新選組が内山を暗殺した動機は、前年、新選組が大阪出張をした際に小野川部屋力士らと乱闘騒ぎを起こした「大阪角力事件」で内山が小野川部屋に協力した疑いがあったことやその吟味が高圧的で近藤との間に確執が起きたための遺恨であるとか、内山が倒幕派志士と結託して米価や油の値を吊り上げていると疑った上での天誅であると言われている。