Fallen Dog God - SLASHDOG-

When unpopular high schooler Issei Hyoudou has a less than romantic encounter with his first-ever girlfriend, the consequences are fatal! As he lies dying, who should come to his rescue but the prettiest girl in school, Rias Gremory! And the shocking truth she shares leaves Issei reeling... "You've been reborn a devil. Now you work for me!" Issei's uproarious life as a devil's minion begins here! (Source: Yen Press) Note: Includes two extra chapters.

Caught with a severe fever, Tobio Ikuse, a second-year high school student, was forced to miss his school trip on a luxury liner with his schoolmates. Four days later, Tobio hears the news about the disappearance of the teachers and second-year students from his school, and it devastates him. A few months after the incident, Tobio, having slowly recovered from the sudden loss of his friends, accidentally encounters one of them again. Chasing after his missing friend Sasaki, Tobio finally manages to catch upto him, but is shocked to see Sasaki alongside a Lizard Monster who attacks him together with the monster. Cornered by the monster, Tobio is rescued by another survivor of the missing luxury liner, Natsume Minagawa, who then hands him an egg before parting ways. Later that night, Tobio finds himself under attack, again, this time by two people with monsters. Amidst all the ensuing chaos, out of Tobio's shadow, came out a Puppy that rescues him. After fending off the two monsters, Natsume once again approaches Tobio before finally deciding to take him to their hideout.