Possibly the most unfiltered portrayal we have from the time period is a racist song parody written by Japanese men mocking the comfort women. With the obvious caveat that I am reprinting it to demonstrate the widespread feelings of Japanese at the time and not to agree with the contents, here is the original. (Translation by /u/Croswam from a previous answer)

雨のショポショポ降るぱん（晩）に カラス（ガラス）のまと（窓）からのそ（覗）いてる まてつ（満鉄）のきぽたん（金）のぱか（馬鹿）やろう

At a night when the rain is falling, from out the glass window, a Mantetsu golden buttoned idiot is peeking in.

さわるはこちせん（五十銭）見るはたた（只） 三円こちせん（五十銭）くれたなら かしわ（鶏）の鳴くまで 付き合うわ

To touch is fifty sen. To watch is free. If you give me three yen and fifty sen I will go with you until the chicken calls. (Until the morning.)

あか（登楼）るの帰るの とうしゅる（どうする）の 早く精神ち（決）めなしゃい ち（決）めたらけた（下駄）もて あか（登楼）んなしゃい

Make up your mind and decide if you will come up or go home. If you decide to enter, pick up your Geta (Japanese wooden clogs) and come up.

お客さんこのころ（頃）紙高い ちょうぱ（帳場）の手前もあるてしょう（でしょう） こちせんしゅうき（五十銭祝儀）をはちみ（弾み）なさい

Dear customer, at this time there is a pimp asking a high price. Come and tip fifty sen quickly.

そしたら私はた（抱）いて寝て ふたち（二つ）もみっち（三つ）もおまけして かしわ（鶏）の鳴くまで ぽぽしゅる（ぼぼする）わ

So hold me and lay down, and I will give you two or three freebies(?). Until the chicken calls (morning) you can use my pussy.

ああたま（騙）されたたま（騙）された こちせん（五十銭）金貨と思うたに ピールピン（ビール瓶）の栓かよ たま（騙）された

Ah I was tricked, I was tricked. I thought it was a fifty sen Gold coin but it turned out to be the cap of a beer bottle. I was tricked.

Some notes on this translation: The entire song is written in a crude dialect, mocking Korean pronunciation. Fifty sen is less than a dollar. Japanese racists thought the way non-native speaker Koreans pronounced “fifty sen” was extremely funny, and it was used as a shibboleth to identify and kill Koreans during the 1923 Kanto massacre. "Mantetsu" is the Manchurian Railroad Company, Japan's major colonial corporation.

We don't have contemporary reactions from Koreans for two reasons: Japanese controlled the printing presses especially after the 1930s, and the Japanese propaganda was that impoverished fathers were selling their daughters into prostitution, which at the time was considered the lowest of professions and not something a Korean nationalist idealist would want to write about.

But we have this Japanese parody, called the "Mantetsu Song" (満鉄小唄), which not only demonstrates the persuasiveness of the propaganda, but also eagerly dehumanizes the supposed singer and degrades her with markers of ethnic difference. It sort of reads like a minstrel song, except that instead of imagining Koreans as happy and nostalgic for old times, it emphasizes the suffering and abuse of comfort women in order to produce joy in the Japanese audience. It's easy to see that comfort women were seen as an inferior species of being, freely available for the Japanese men to abuse. If you read debates about the comfort women system you will see all manner of primary sources that Japanese created at the time to whitewash what they were doing, but I have never seen this song mentioned.

While this dehumanization seems to have been widespread and dominant, it was not all-pervasive. The 1958 Japanese novel and 1959 film The Human Condition (人間の條件), made just 11 years after Japan's surrender, portrays comfort women as victims of the capitalist and colonialist systems, robbed of their freedom but trying to make the most of their situation. We can see that the veteran who wrote the novel The Human Condition, Gomikawa Junpei, was more observant about comfort women than most Japanese soldiers.

Unfortunately, though, in both Japan and Korea, the consensus view was that comfort women did not deserve to be thought about or remembered; that their dignity had been taken away from them by their fathers, basically. Again, this narrative was perpetrating the Confucian dogmas of both countries. It was only in the 1980s that Koreans started to see comfort women as victims of Japanese rape, rather than as selling themselves out to the Japanese.

While more can always be said and the estimated statistics by historians have differed significantly, I summarized the very basic information on "comfort women" and the their estimated statistics before in: Were some ethnic Japanese women comfort women themselves in WW2?