Drawing evidence from Korean, I argue that the argument-introducing heads Voice (Kratzer 1996) and Appl (Pylkkänen 2008), which are reduced to i* (Wood & Marantz 2017), assign honorific (HON) case markers to the nominal argument in their specifier position. While direct objects (DOs) are not eligible for an HON case marker, subjects, indirect objects (IOs), and vocative noun phrases are. To gain further evidence that the Spec-head configuration is necessary for HON case assignment, I provide a full account of the distribution of case in Korean. My analysis of vocative noun phrases lends support to the claim that A-properties can be observed in CP, which is often assumed to be an A’-domain (see Obata & Epstein 2011 and van Urk 2015, among others). Cross-linguistic evidence is presented from Meadow Mari (Uralic), southern dialects of Basque (Isolate), Galician (Romance), Lebanese Arabic (Semitic), among other languages. A theoretical implication of this thesis is that the subject and the IO can be grouped together to the exclusion of the DO. An additional implication is that discourse participants such as the addressee are represented in syntax (see Speas & Tenny 2003, Haegeman & Hill 2013, Miyagawa 2017, 2022, Portner et al. 2019, among others). Under my analysis, what is often referred to as the Speech Act Phrase (SAP) boils down to either VoiceP or ApplP. Hence, I emphasize that argument-introducing heads can be introduced beyond the thematic domain in syntax (see Tsai 2018, Spadine 2020, Ritter & Wiltschko 2019, among others).