Koukyuu Ichiban no Akujo

Rinrei, who has a plain face, transforms with makeup. Normally Rinrei is plain and quiet, but when she puts on makeup, her heart is brightened and she becomes a confident and beautiful woman. Rinrei loves cosmetics, and her love for them has led her to develop cosmetics herself, which become popular products in the capital. However, worried that this will cause her to miss her chance to get married, her father schemes to have her taken to the harem...

(Source: Kadokawa, translated)