The plot could involve a glitch that merges the two worlds. Undertale characters start to show up in the DDLC world and vice versa. Frisk could end up in the DDLC clubroom and be really confused. The DDLC characters could be scared or intrigued by Frisk's determination and ability to reset. And in the Undertale world, the DDLC girls' presence could disrupt the normal flow of things. For example, Monika's attempts to manipulate the situation could accidentally set off some of the more dangerous monsters in Undertale, leading to a whole new adventure to fix things.
One interesting plot could be that the main character from DDLC, say, the protagonist, gets transported into the Undertale universe. They could start in the Ruins and interact with Toriel. Since the DDLC character is used to a different kind of world, their reactions to the monsters and the unique magic in Undertale would be fun to explore. Maybe they could try to use their knowledge from DDLC to solve some of the problems in Undertale, like trying to understand the nature of EXP and LOVE in the context of their own experiences.
A possible plot is that the DDLC girls somehow end up in the Underground. Monika, being the self - aware one, might try to take control of the situation in a similar way she did in DDLC. But in the Undertale world, she has to deal with Sans, who can sense something is off about her. Meanwhile, the other DDLC girls are trying to find a way home while also befriending the friendly monsters like Papyrus. This could lead to a lot of comical and interesting interactions as the two very different universes collide.
Chapter 90, "Toward The Southern Atholor Continent I", is the clearest early answer because the buildup finally cashes out in a real clash. The chapter turns that into something concrete by moving from The first light of morning crept over Elderglow Academy, casting a... to I don't think he honored the invitation without purpose." Dean....
Chapter 118, "Caught In A Pinch II", is the clearest early answer because it turns Damien's situation into a concrete plot event. The chapter gives readers a real answer by opening on The forest echoed with the sounds of battle as Damien continued his... and ending on Despite the odds, Damien's skill and strategy prevailed.. In story terms, the chapter closes with Narna's excitement was replaced with fear, and Keith gritted his teeth, drawing his blade.
Chapter 103, "I Don't Plan On Failing I", is the clearest early answer because it turns Damien's situation into a concrete plot event. The setup is The campfire crackled softly, casting flickering shadows over the..., but the pressure keeps building through Damien sat on a fallen log near the fire, throwing more dried up wood....
Chapter 471, ", Victory Strategy", is the clearest early answer because it turns Green Skin's situation into a concrete plot event. It opens with Green Skin Orcs, of course, had no need to rule over humans. and closes on Gu Hang, of course, still had to guard against the main Green Skin.... The key payoff is that the danger stops being abstract and the conflict around Green Skin becomes immediate, forcing the surrounding cast to react under pressure.
Chapter 47, "Actively Hunting IV", is the clearest early answer because it turns Magic Essence's situation into a concrete plot event. The chapter turns that into something concrete by moving from Swooosh… Before Damien could understand what was happening, dozens of... to It continued to climb higher and higher, the whole area feeling a....
Chapter 143, "Demon Infestation Mission IV", is the clearest early answer because it turns Damien's situation into a concrete plot event. The chapter gives readers a real answer by opening on Damien rode Aquila back to the town in the same way he'd left—swiftly... and ending on All set." Damien noticed how focused she was during the process, and....
Chapter 458, ", you dare too?", is the clearest early answer because it turns Gu Hang's situation into a concrete plot event. It opens with Could living on 600 Tax Currency a year starve him to death? and closes on In the past, already a Planetary Governor, would he really have been.... The key payoff is that the chapter closes with Still owe 59k, which gives Gu Hang a stronger narrative position and pushes the power growth onward.
Chapter 439, ", Temir No.5 Meat Grinder", is the clearest early answer because it turns Green Skins's situation into a concrete plot event. A useful checkpoint is the way the scene starts with Soon, just a few days later, Du Shiliang's United Fleet had been... and follows through with ———— 6k Still owe 62k Paying debts is so hard....
Chapter 489, ", Deadly Assassination", is the clearest early answer because the violence around Deadly Assassination becomes final instead of hypothetical. The setup is This situation is of no concern to the Imperial Guard., but the pressure keeps building through What exactly does The Imperial Guard protect within the Terra....
Chapter 27, "Burning Through Essence", is the clearest early answer because it turns Damien's situation into a concrete plot event. Early on, Damien thought for a moment before coming up with a feasible solution.... By the end, Only Damien remained standing upright and this was because of the.... Inside the broader power growth storyline, the chapter closes with However, the only thing that mattered to Damien was obtaining the Monstrous Wolf.