Kare no Aijou no Hakari

Arishige Ritsu is the most popular boy in Nagao Mioko's high school -- admired by the boys and adored by the girls. His smile has the power to charm many, but Mioko has a strange feeling about it. When the whole school discovers Arishige's secret, Mioko must decide what role she wishes to play in the life of the boy whose honest and patient personality she has grown to love...

The manga also contains two unrelated oneshots.

(Source: Sound of Jewels)