D.N.Angel, Vol. 4 by Yukiru Sugisaki

Daisuke's news friend, Takeshi, is into getting the latest scoops about Dark. On one heist, he sneaks into the museum to find the Phantom Theif, but instead finds a beautiful girl instead. Takeshi returns the next night, swearing to protect her from Dark who is after the girl's pendant. Later, Daisuke's class is off to an island on a field trip. With fun activities to do, it's sure to be a blast, but when Riku finds Risa and Daisuke in a compromising position that was completely accidental, the young girl who has fallen for Daisuke is heartbroken. Then Daisuke meets Satoshi's other self and Dark's other, evil half - Krad.