Milky Cartoon Anime

The first series is a set of 25 stories about a male businessman arriving at the hotel after taking a train home from work. He encounters the mysterious owner of the hotel, an old mouse known as Gregory, who suggests that he stay a while. Soon, the man becomes drawn into a bizarre series of events taking place within Gregory House as he tries desperately to escape from this bizarre purgatory.

(Source: Wikipedia)

Based on the online mobile phone otome game "Sengoku☆Paradise".

The first 3 minutes of the 10 minute spot for Sengoku☆Paradise Kiwami is the anime. The rest of the 7 minutes is of Sengoku☆Paradise Kiwami cast Daisuke Namikawa and others (first time with Tetsuya Kakihara, second time with Rei Mochizuki) going on missions, plus an informative short.

(Source: AniList.co)

The third series, The Last Train is set with 26 stories during a bizarre train ride that Gregory embarks upon.

(Source: AniDB)

The second series, The Second Guest is similarly set with 25 stories, except this time the main victim is a woman who has just taken a taxi home from her best friend's wedding ceremony.

The fourth series, The Bloody Karte (presented as a side series on the DVDs) is a set of 12 stories about Catherine working in a mysterious hospital.

(Source: AniDB)

Three unbroadcasted exclusive Special shorts of Gregory Horror Show (presented as bonus videos on the first series DVDs volumes 1-3 in Japan only), containing stories featuring Gregory himself as a guide, giving his commentary and thoughts on each of the guests in the hotel, also displaying paintings based around the said guests.

(Source: Wikipedia)