Firstly, those are some fantastic manga there, especially Witches, Children of the Sea and Sexy Voice & Robo. Incidentally, Ikki, the same magazine Children of the Sea runs in also has quite a few interesting releases as well, so you might want to check them out.
I've always found Victorian Romance Emma to be similar in terms of atmosphere and pacing with Yokohama Kaidashi Kikou. This goes the same as well to
Yuki Urushibara’s one-shots
There’s, of course, Iou Kuroda’s
Japan Tengu Party Illustrated and
Nasu. Similar to Kuroda’s heavy art style is
Baka to Gogh, though a bit more idealistic and goofy but no less charming.
The Yellow Book is a fascinating read as well, filled with subtelties and heartwarming range.
Kyoko Okazaki's works are some of the most ambitious ones I've ever read, though they could be a bit dark and grotesque for some, namely
Helter Skelter and
River's Edge, which are filled with nuanced characters and provoking themes.