1. A network system, comprising: a first communication device; a second communication device composed separately from the first communication device; and a server comprising a keyword database, wherein the first communication device comprises: a first input device that allows a user to input a keyword; and a first search device capable of carrying out a first search process that includes sending the keyword input to the first input device to a search engine and receiving a search result, wherein the keyword database cumulatively stores a plurality of keywords used for a plurality of first search processes, wherein the second communication device includes a printing function, a scan function or a combination thereof, and the second communication device comprises: a second input device that allows a user to input a part of characters included in a character string composing one word; a keyword acquisition device capable of acquiring, when only the part of characters is input to the second input device, a specific keyword including the part of characters input to the second input device from the keyword database which is cumulatively storing the plurality of keywords; and a second search device capable of carrying out a second search process that includes sending the specific keyword acquired by the keyword acquisition device to a first search engine and receiving a search result, wherein the server further comprises a keyword identifying device that identifies, from the keyword database, the specific keyword including the part of characters input to the second input device, and wherein the keyword acquisition device acquires the specific keyword identified by the keyword identifying device.