Youji Takashima is a high schooler with a major 'sister complex' towards his older sister, Senko, 26, whom he's living with... One day, she introduces him to one of her old friend from college: Ren Akishima. Their first meeting doesn't go as expected, Youji doesn't like Ren and starts to think that he wants to marry his sister. Later, Senko reveals that she's leaving for NY to get some advancement in her job and that she intends to leave Youji with Ren. (from EoP website)

Keinoshin and Shotaro are students who spend their after school hours as Dark Hunters. Darkness and light both exist in the world, and it is their job to protect the balance between them. Kei and Sho used to be close friends when they were little, but now they are only reluctant partners. At school, they're seen as opposites--the cool and aloof Sho and the cute and friendly Kei. However, they must work together if they want to stop the forces of darkness. Their first case of the manga involves the mysterious vanishing of many cats and dogs in the area, and a second involves a little boy who can see the 'ghost' of an old homeless man he had befriended.(from mangaupdates)