Kakunyo 覚如, the great-grandson of Shinran 親鸞, produced the biography of Shinran called Shinran denne 親鸞伝絵, but the first book was lost. He revised the book many times and there are 5 revised editions extant.
The Mōsu 帽子 garment is one of the characteristics of Shinran. Among 5 revised editions, in the Rinna-bon 琳阿本, the Takada-bon 高田本 and the Gugan-bon 弘願本, there are two facts made clear about the Mōsu. Namely, Shinran wears a Mōsu, but he sometimes takes it off, and second, many monks also wear a Mōsu. Accordingly, in these 3 revised editions, Kakunyo thinks that the Mōsu of Shinran is one of the protections against cold, like the Mōsu of other monks.
On the other hand, in the Kōei-bon 康永本 and the Shōganji-bon 照願寺本 (the contents of which agree with each other), the monks who wear a Mōsu are few, and thus the Mōsu of Shinran is impressive. The scene in which Shinran keeps wearing a Mōsu is from the scene Inadakōbō 稲田興法 (下巻 第二段) until before his death in the scene Rakuyōsenge 洛陽遷化 (下巻 第六段). What is Kakunyo’s view on the Mōsu of Shinran in the Kōei-bon in the final complete edition?
In the Kōei-bon, Shinran wears a Mōsu on his journey and at the place of his sermon. And in the scene Rennimusō 蓮位夢想 (上巻 第四段), for the title of honor given to Shinran, Kakunyo uses Soshi shōnin 祖師聖人 to refer to him as the founder of the Shinshū 真宗 sect. For these reasons, I think that, in the Kōei-bon, the Mōsu of Shinran is the symbol of Shinran who continues his journey for the propagation of his teachings as the founder of the Shinshū sect.