Shuichi and Chiaki have never met in canon nor in the UTDP, which makes shipping this for the canon moments they've had utterly impossible. Shuichi has seen Chiaki in person, although that was Tsumugi cosplaying her.
They are very similar personality wise; both being very smart, this is shown for Chiaki with her being a big part of finding the blackened in Danganronpa 2: Goodbye Despair, and for Shuichi this shown with him being the second Ultimate Detective and finding out who the mastermind of Danganronpa V3: Killing Harmony is. Another very similar trait between the two, is their constant second guessing of themselves, with Shuichi not being a very confident person and often being unsure/unconfident of his claims, (despite them being right most of the time) and this personality trait being shown with Chiaki is after she makes a statement and/or claim the sentence is often followed by "...I think"
Appearance wise they're not very similar, being opposite genders, though the traits they do share is their rather dark clothing with Chiaki wearing a dark teal cardigan, with a couple other things being the color as well, Shuichi is wearing all black, with some white buttons. They are also both wearing school uniforms, while Chiaki is wearing hers under her cardigan. Though that is only AI Chiaki.
Some people, despite the lack of canon, ship this anyway. The main reason is probably for the dynamic, as Shuichi is usually seen as timid and reserved, and Chiaki is usually seen as an optimistic and reassuring. Their dynamic could work extremely well regarding Shuichi's character development, with Chiaki's heart-warming reassurance constantly being given to him.
The ship is not very popular at all, with there being close to no fan art with the two alone and almost no fan fictions on AO3 as well this ship is easily overpowered by Shuichi's more popular ships; Saimatsu, Saiouma, and Saimota, and Chiaki's more popular ships; Hinanami, and Komanami.