Looking for

http://www.mangago.me/read-manga/boku_to_neko_to_hatsukoi_kousa/
http://www.mangago.me/read-manga/hachimitsu_darling/
http://www.mangago.me/read-manga/kuroneko_wa_shippo_de_amaeru/
This one's a little depressing: http://www.mangago.me/read-manga/mahoroba_no_hibi/

http://www.mangago.me/read-manga/bijo_to_chinjuu/
http://www.mangago.me/read-manga/kuroneko_wa_shippo_de_amaeru/
http://www.mangago.me/read-manga/toiki_yori_mo_yasashii/
http://www.mangago.me/read-manga/ousama_ni_kiss/
http://www.mangago.me/read-manga/shiawase_no_level/
http://www.mangago.me/read-manga/harapeko_usagi_to_koisuru_ookami/
http://www.mangago.me/read-manga/kamatte_kawaii_hito/
http://www.mangago.me/read-manga/gravity_eyes/

or do you mean shapeshifter kind of pets? like
http://www.mangago.me/read-manga/if_dogs_could_also_walk/

http://www.mangago.me/read-manga/sugar_code/
http://www.mangago.me/read-manga/konbini_kun/
http://www.mangago.me/read-manga/aiso_tsukashi/

about 9 pages then I realized why was it's depressing.