Радуют меня эти забугорные фанфик-райтеры. Какие они пишут дисклэймеры!
There is no safe sex in this story. This is because
a) Tatsumi and Watari lived in times when AIDS was not yet an issue.
b) Now, Tatsumi and Watari are both dead and I believe Shinigami are therefore unlikely to contract STDs or HIV. In real life, condoms are your friends and protect you and your partner. Better be safe than sorry.