I put that citation into the Wikipedia link. It came from a grammar book in Japanese published by Hitsuji Shobou. It lists Japanese cases, giving the particle that marks the case (or showing a zero crossed through for the nominative case), gives some Japanese names for the cases, and gives the English name for the cases.

I think some confusion regarding the so-called bare case may result from the frequent use of は "wa." To eliminate that confusion, one should remember that "wa" does NOT mark case:

http://www.nkc.u-tokyo.ac.jp/study_info/study_info01_04_e.html

The agentive case is similar to the nominative case, but as I understand it marks the "agent" of the sentence, that is, the actual noun that performs the action of the verb or has the attribute of the predicate (or in the case of a passive verb, receives the action of the passive verb). This construction makes sense in a topic prominent language like Japanese.

For completion, here is a particle-English name (formal Japanese name) table of cases taken from that source (using the pronunciation, not the spelling of the particle, when romanized):

(ø), nominative（名格）;

が/ga, agentive（主格）;

を/o, accusative（対格）;

に/ni, dative（与格）;

へ/e, allative（方向格）;

で/de, locative-instrumental（所‐具格）;

と/to, commitative*（共格）;

から/kara, ablative（奪格）;

まで/made, terminative（とどき格）;

までに/made ni, limitative（かぎり格）;

の/no, genitive（属格）

*Normally, this is called "comitative," but in my source is written with 2 m's as "commitative."

It then lists cases that involve the genitive being combined with another case (such as への), but I won't list that here. Those who have studied Latin may be confused by the designation of the ablative, but should keep in mind that the "proper" ablative simply specifies the origin of an action or something from which something separates; Latin expands the ablative by also including the locative (where something occurs) and instrumental (the means by which something occurs) aspects, speakers relying on prepositions to tell the difference. Note also that "wa" is not listed here; on the following pages (pp. 28-29), the book lists the different ways that cases are marked when accompanied by "wa": For the nominative, は "wa" is simply added; for the agentive and the accusative, the case particle is replaced by は; for all the others (excluding the genitive), は is tacked on after the case particle.

The book is written in Japanese, but English translations were given for the cases. Source: Takahashi, Tarou et al. (2010). A Japanese Grammar (in Japanese) (4 ed.). Japan: Hitsuji Shobou. p. 27. ISBN 978-4-89476-244-2.