I don't think it's NTR. It' isn't Takuji's way. We don't know the story, maybe that black guy is just kiss her, and she's forced to marry him because of her parent's order or something. Because before fucking her in this chapter, I think the guy having a serious conversation with her about this wedding and their love. The girl looks loved him , not the black guy too. Anyway, we have to wait for translated version.
In the previous chapters, every page is filled with hot and sweet lovemaking between risa and the protagonist with black hair and glasses. There's no doubt she loves him for saving her from drowning i think, when they were kids and she came up to him and confessed in the most direct manner possible ;)
This dark skinned dude appears out of nowhere, it makes me wonder if they indeed have any conversation on previous chapters like user "dorarado" mentions, about arranged marriage between her and the dark-skinned guy's families. The kiss could be interpreted as a signal of what's inevitable, NTR, but, in several vanially non-hentai series, there's this situation where a villain kisses the love interest of the protagonist against her will, and eventually everything gets sorted out into an happy ending without having to soil the maiden, so considering that, and knowing Takuji-san's style of storytelling, i doubt this will turn into a disgusting NTR. Let's hope and wait for translations.
There is actually a conclusion to this. However, no one can find any raws or even the magazine that it's in. Pity, I heard that the next chapter is happier.