Interesting, the Japanese word for "watermelon" ("スイカ" / "suika") is commonly written in katakana (as are most plants and animals in modern Japanese), so you nornally just get the pronunciation when reading it. That's how it's written here.
"Sui"/"水" is the common Chinese derived pronunciation for "water" in most compound words, and "ka"/"瓜" means "melon". As a result, in my mind, I always figured it was just "水瓜" / "watermelon" just like it is in English.
Thinking that way made the fact that the artist explicitly pointed out the English etymology in the post here as trivia seem a little weird to me, since it wouldn't be that interesting if it just matched the Japanese etymology.
Apparently, "水瓜" is a possible alternative kanji spelling in Japanese, but its rare, and the original / preferred / more proper kanji spelling is "西瓜" meaning "western melon" which has the same pronunciation.
So, watermelon day, huh? It's my favorite fruit, I didn't knew there was a holiday dedicated to it. Once again, youmu-kun introducing me to holidays I didn't knew!
From left to right : Militech Mk.31 HMG, Nokota D5 Copperhead, Budget Arms Carnage and Militech M251s Ajax.
Edit: I just noticed Shiroko seems to have Errata (the unique thermal katana) strapped to her left hip, so I'm tagging it in, also removed minigun and gatling gun and added heavy machine gun, because the MK 31 is a single barrel gun.
Welp. It's over. The night, and the dream, were long, but life is only beautiful because it's so transient. Yet brilliant, so beautiful, it enchants us, to the point of obsession.
Glancing over the fan wiki it seems like it might be implied, but not openly stated.
As for what is open:
Trivia
On the Global server of Project SEKAI, Mizuki is referred to with both "she/her"and "they/them" pronouns, though it is unknown which Mizuki personally uses. When possible, Mizuki's name is used in place of pronouns entirely.
On the Japanese server of Project SEKAI, Mizuki typically uses the masculine first-person pronoun Boku (ボク), which is most often used by immature or young boys, though it is also used by tomboyish girls.
@TrueAether It's Monna not Lynn. Monna has brown short hair and Lynn has long black hair. Monna's hair would be visible in the screenshot in the art, but it's not. It's brown short hair right at the top of the screenshot.
Here's a screenshot of the scene I grabbed from a video. Notice it's Monna standing to the left of Ellen.