"MOMA SUI" seems to mean "They(singular) are/will/should" or "Another person" + "declaration". We don't know if they have "he/she" or only "they". This might double as the plural form if they don't have one.
In this chapter she may be talking to the villager after calling out to Ryuu, saying something like "He is over there" or "He is awake"
I based this on the two times Myaa-san leaves the cave in chapter 1-pg23 and 4-pg5.
In chapter 1 Myaa-san is thinking out loud. "He shouldn't leave". She says the same thing in chapter 4 before tell him to stay.
"MOMA SUI NAOUPU TUI AII-" - He should stay TUI AII"
"IMU SUI" meaning "I am/will/should" or "I" + "declaration".
"IMU SUI, NIMA" - I will go.
"GOSU SUI" meaning "You are/will/should" or "You" + "declaration".
"GOSU SUI, NAOUPU"- You will stay.
I think most of this is definitely plausible, except for the part about
imu sui and
gosu sui.
I'm inclined to think of them as pronouns: since
imu by itself means "all right" / "yes" / "proceed," having
sui mean "will" / "[declaration particle]" would be a bit of a mess. We also know from Miyamutuu's simplified language that
imu sui and
gosu sui almost certainly belong to the same part of speech. So,
imu sui = "me" and
gosu sui = "you."
However, my theory is weakened by the fact that
sui really does seem to function as a particle, as reflected by its frequency of occurrence... In fact, I feel like my theory is likely wrong...
My brain hurts