Every anime has a beach episode. I think it's a law somewhere. 

This piece was done in a modern shin-hanga style, which was dominant in the early 1900s at the peak of Japanese woodblock technique. Shin-hanga prints are known for their atmospheric realism, and require many dozens of impressions with hand-carved wood blocks. It was a ton of work to make those prints, but the low yen compared to higher valued European currencies in the early 1900s made it economically viable. 

The left caption translates to 'pocket' and 'monster'. 

The right caption is an excerpt from the Kojiki, one of Japan's oldest written works from the early 700s. The line translates to 'I vow that I shall catch'.