Board Thread:Questions and Answers/@comment-92.97.106.194-20131016142828/@comment-16383347-20131016150047

there is no proper manga for it there are prequels,sequels,anthology and cardinal anthology for each character with different stories.

Prologue:

  http://toudou.tumblr.com/post/48195958349/scanlation-diabolik-lovers-prequel-prologue-by

you can read prequels here :

Shu's prequel

http://sakamakireiji.co.vu/post/49836717259/scanlation-shuus-prequel-chapter

Ayato's prequel

  http://narihira.tumblr.com/post/42310261877/scanlation-of-ayatos-prequel-chapter

Kanato's prequel

  http://narihira.tumblr.com/post/47182693546/scanlation-of-kanatos-prequel-chapter

Laito's prequel

http://imgur.com/a/1EBRh

Reiji's prequel

  http://toudou.tumblr.com/post/42263459647/scanlation-sakamaki-reiji-chapter-first-part-by

Sequels:

Shu

http://sakamakireiji.co.vu/post/63716742152/scantalation-shuus-sequel-chapter

Ayato

  http://narihira.tumblr.com/post/49885572567/scanlation-sakamaki-ayato-sequel-by-suzaka-shina

Kanato

  http://narihira.tumblr.com/post/49626803705/scanlation-sakamaki-kanato-epilogue-by-carawey

Laito

http://imgur.com/a/HnjDa

Reiji

http://toudou.tumblr.com/post/47099421790/scanlation-sakamaki-reiji-chapter-end-part-by

Currently no prequel or sequel for subaru :/

Anthologies

http://www.mangahere.com/manga/diabolik_lovers_anthology/

Cardinal Anthology

Ayato  http://narihira.tumblr.com/post/39704034751/this-is-my-own-translation-scanlation-of-one-of

Reiji  http://vocaotome.tumblr.com/post/37821699218/toudou-sweet-x-sugar-by-toshimitsu-megumi-from

2. http://toudou.tumblr.com/post/43561233231/more-crazy-by-yanagiya-maro-from-the-diabolik

Subaru  http://anekofoxx.tumblr.com/post/61228687272/hi-there-here-is-my-translation-of-subarus

Shū  http://anekofoxx.tumblr.com/post/62431585329/shus-chapter-from-cardinal

Kanato  http://anekofoxx.tumblr.com/post/61735838628/kanatos-chapter-from-cardinal

No cardinal chapter for Laito yet

Note:If you want to know about Mukami brothers you can see there drama cd's translations on this wiki

Hope it helps!