In order to achieve the basic commercial objective of selling products, it is considered important that customers feel comfortable shopping at a store.Providing comfort is expected to increase customers' willingness to buy, which in turn will lead to higher sales. Higher ceilings are expected to have a positive impact on users, but it is difficult to actually change the ceiling height. Therefore, we verified that using MR to simulate the perception of ceiling height has the same effect as actually changing the height of the ceiling.In this study, an HMD (head-mounted display) is used.Preliminary experiments compared three types of ceilings: "normal ceiling," "monochromatic: blue ceiling," and "blue sky ceiling," and suggested that the "blue sky ceiling" enhanced the feeling of openness and comfort the most.On the other hand, "monochromatic: blue ceiling" tended to give a feeling of discomfort and oppression.An additional experiment at this university co-op confirmed the possibility that "blue ceiling" not only increases attention to the ceiling, but also positively influences purchasing behavior.Conversely, "monochromatic: blue ceiling" decreased appetite, suggesting that color may influence purchasing behavior.