I consider here the significance of the expression “ojo wo togu” in Tannisho Chapter III considering how it differs from the expression “ojo wo su” in the Daigo Honenshonin-denki and the Kudensho of Kakunyo.
A verb “togu” expresses the difficulty of a desire, an intention or an act, of the subject. However, it cannot be said that the distinction in expression of “togu” and “su” in the phrases “ojo wo togu” and “ojo wo su” is clear in contemporary literary works and Buddhist sermons.
In Shinran's usage, expressions with “togu” tend to be related to the Primal Vow and the Other Power of Amida Buddha. Especially relevant is the phrase “Kasui no Gan” and in comparison with the “ojo wo togu” in the Tannisho we may place an example in the Yuishinsho-Mon'i.
In conclusion, strongly related with expression of “ojo wo togu” is the term “eshin” is used in Chapter III. This expresses the character of this chapter. This chapter is able to express the overall structure of the salvific capacity of the Pure Land teaching, grounded in the Primal Vow, in common with Shinran's expression.